<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:a107faeb-8e93-4b75-97cc-5d2b8892c56e,g:ac8880ee-0085-4766-b35b-acba0e6a7ca5-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="onit-20240930.xsd#UNAUDITEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_b0537950-d7f6-4d15-8667-b12687206d10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_StatementTable_b0537950-d7f6-4d15-8667-b12687206d10" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_9986dbd4-3666-47bb-9baf-0d31c44caa23" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b0537950-d7f6-4d15-8667-b12687206d10" xlink:to="loc_srt_ConsolidatedEntitiesAxis_9986dbd4-3666-47bb-9baf-0d31c44caa23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_9986dbd4-3666-47bb-9baf-0d31c44caa23_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_9986dbd4-3666-47bb-9baf-0d31c44caa23" xlink:to="loc_srt_ConsolidatedEntitiesDomain_9986dbd4-3666-47bb-9baf-0d31c44caa23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_ecfdb239-c5e9-42f0-bf66-548425212259" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_9986dbd4-3666-47bb-9baf-0d31c44caa23" xlink:to="loc_srt_ConsolidatedEntitiesDomain_ecfdb239-c5e9-42f0-bf66-548425212259" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_598f0904-5666-4f12-bc93-902c4d29ed21" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_ecfdb239-c5e9-42f0-bf66-548425212259" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_598f0904-5666-4f12-bc93-902c4d29ed21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c220d6c6-0d7a-4ef0-a589-91346723b8d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_b0537950-d7f6-4d15-8667-b12687206d10" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c220d6c6-0d7a-4ef0-a589-91346723b8d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_c220d6c6-0d7a-4ef0-a589-91346723b8d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c220d6c6-0d7a-4ef0-a589-91346723b8d7" xlink:to="loc_us-gaap_RelatedPartyDomain_c220d6c6-0d7a-4ef0-a589-91346723b8d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_5748ec15-e060-4063-9e03-8164471eed1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c220d6c6-0d7a-4ef0-a589-91346723b8d7" xlink:to="loc_us-gaap_RelatedPartyDomain_5748ec15-e060-4063-9e03-8164471eed1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_93711fba-0a65-4adb-943f-4115ab4fada1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_5748ec15-e060-4063-9e03-8164471eed1b" xlink:to="loc_srt_AffiliatedEntityMember_93711fba-0a65-4adb-943f-4115ab4fada1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_36ae3051-d95b-4209-b2c6-eaeda5fd86c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_36ae3051-d95b-4209-b2c6-eaeda5fd86c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_Advances_70f5fe87-e1d7-448d-96d3-e85ee4ab20cb" xlink:href="onit-20240930.xsd#onit_Advances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_onit_Advances_70f5fe87-e1d7-448d-96d3-e85ee4ab20cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_a0d14fd4-4972-41fa-aa70-2dd844a99529" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_a0d14fd4-4972-41fa-aa70-2dd844a99529" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_9cb0d40d-2b6e-42f9-93ca-1e8958849e26" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_9cb0d40d-2b6e-42f9-93ca-1e8958849e26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_f286b603-bfca-40ca-b464-a26206ac5eaa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_f286b603-bfca-40ca-b464-a26206ac5eaa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_59d8aed6-a31c-4bdf-85d6-3ee392a8cf1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_OtherReceivables_59d8aed6-a31c-4bdf-85d6-3ee392a8cf1b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsFairValueDisclosure_ea0bb452-7e40-4113-b624-f79042371732" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_OtherAssetsFairValueDisclosure_ea0bb452-7e40-4113-b624-f79042371732" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_df133851-4887-4ec8-bad4-a904f2d38195" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_OtherAssets_df133851-4887-4ec8-bad4-a904f2d38195" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherFinancingLiabilities_752d7c21-233d-4c27-99f2-62eb09210fba" xlink:href="onit-20240930.xsd#onit_OtherFinancingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_onit_OtherFinancingLiabilities_752d7c21-233d-4c27-99f2-62eb09210fba" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_aad9b1ac-e5fc-41e3-8622-ed621f93832c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_aad9b1ac-e5fc-41e3-8622-ed621f93832c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermBorrowings_f499fe39-9870-4d0f-bcdd-1e8c2c4a4b52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_OtherShortTermBorrowings_f499fe39-9870-4d0f-bcdd-1e8c2c4a4b52" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_36804910-8052-4eaa-be90-b43124e6a615" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_SeniorNotes_36804910-8052-4eaa-be90-b43124e6a615" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_a3a2f8a5-3884-4335-97f9-e63bdd8b10ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_OtherLiabilitiesFairValueDisclosure_a3a2f8a5-3884-4335-97f9-e63bdd8b10ba" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_83db624c-1258-4386-9fdb-f371cee16a1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_83db624c-1258-4386-9fdb-f371cee16a1d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_8a73f204-d793-4440-b654-116dfc73e8d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_8a73f204-d793-4440-b654-116dfc73e8d8" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_d0f0cf6f-77f1-4fb3-8fce-70585577fae4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_CommonStockSharesIssued_d0f0cf6f-77f1-4fb3-8fce-70585577fae4" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_e5e16925-de60-4e1d-99a6-ab546ffe496d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8eed8949-43b1-4df2-982e-d30b2e6f8cad" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_e5e16925-de60-4e1d-99a6-ab546ffe496d" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="simple" xlink:href="onit-20240930.xsd#UNAUDITEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_0bdb5362-0873-4263-a487-f9605e0b9ec9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_StatementTable_0bdb5362-0873-4263-a487-f9605e0b9ec9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_20fa1dde-7e88-43be-bd01-2d5d6b86414e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_0bdb5362-0873-4263-a487-f9605e0b9ec9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_20fa1dde-7e88-43be-bd01-2d5d6b86414e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_20fa1dde-7e88-43be-bd01-2d5d6b86414e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_20fa1dde-7e88-43be-bd01-2d5d6b86414e" xlink:to="loc_us-gaap_EquityComponentDomain_20fa1dde-7e88-43be-bd01-2d5d6b86414e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_20fa1dde-7e88-43be-bd01-2d5d6b86414e" xlink:to="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_efab9a1d-4298-465e-82fd-df82b7b51c34" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:to="loc_us-gaap_CommonStockMember_efab9a1d-4298-465e-82fd-df82b7b51c34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_97a54b20-1b4e-4f8c-803a-f4db5374ea97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_97a54b20-1b4e-4f8c-803a-f4db5374ea97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_e43ccd1d-9b6a-47ee-9dd5-c3790355d58a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:to="loc_us-gaap_RetainedEarningsMember_e43ccd1d-9b6a-47ee-9dd5-c3790355d58a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1c3d02c7-25d3-4a49-9e55-a11142a80d64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1f066c52-68ec-4d89-91a0-b82532b2119a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1c3d02c7-25d3-4a49-9e55-a11142a80d64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_fea5b744-7b87-48ec-93ff-b840666129e0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_fea5b744-7b87-48ec-93ff-b840666129e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_26c7881c-a2c9-4035-b9be-011dbd61f8da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_26c7881c-a2c9-4035-b9be-011dbd61f8da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_fe780eb9-f514-44d9-a4d5-fa6377b8bdaf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_NetIncomeLoss_fe780eb9-f514-44d9-a4d5-fa6377b8bdaf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_a8248b79-d20e-4583-b7d5-9784ea2405d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_a8248b79-d20e-4583-b7d5-9784ea2405d8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_ddaddc0b-3ed2-49f0-bac4-916a147b4af4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_ddaddc0b-3ed2-49f0-bac4-916a147b4af4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_ce9b050f-4885-4b99-b92a-91e2975efad9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_229c5c7a-f6c3-4d18-b1ed-9e8190caf048" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_ce9b050f-4885-4b99-b92a-91e2975efad9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_ad61a43c-4013-461f-8a40-34e15bd9e610" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_085bed19-739d-4cdb-ad2f-a5f9c93a1dd0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFOPERATIONSParenthetical" xlink:type="simple" xlink:href="onit-20240930.xsd#UNAUDITEDCONSOLIDATEDSTATEMENTSOFOPERATIONSParenthetical"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/UNAUDITEDCONSOLIDATEDSTATEMENTSOFOPERATIONSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e21af108-e2ac-45ad-8c0a-e3eaa0edcc6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_90bc5469-e3d7-4660-be70-ab3375bd4a80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e21af108-e2ac-45ad-8c0a-e3eaa0edcc6d" xlink:to="loc_us-gaap_StatementTable_90bc5469-e3d7-4660-be70-ab3375bd4a80" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1aa90f92-b400-4dfc-b754-9673fd76611c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_90bc5469-e3d7-4660-be70-ab3375bd4a80" xlink:to="loc_us-gaap_DebtInstrumentAxis_1aa90f92-b400-4dfc-b754-9673fd76611c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1aa90f92-b400-4dfc-b754-9673fd76611c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1aa90f92-b400-4dfc-b754-9673fd76611c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1aa90f92-b400-4dfc-b754-9673fd76611c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bfb93994-09ea-4e3e-8bd4-6c6babbcc1ef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1aa90f92-b400-4dfc-b754-9673fd76611c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bfb93994-09ea-4e3e-8bd4-6c6babbcc1ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorSubordinatedNotesMember_cc9ef377-18cc-4f77-a6e2-179f60b2fd9f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorSubordinatedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bfb93994-09ea-4e3e-8bd4-6c6babbcc1ef" xlink:to="loc_us-gaap_SeniorSubordinatedNotesMember_cc9ef377-18cc-4f77-a6e2-179f60b2fd9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e54fa48f-7ee8-4ef4-944e-3ca026f77e68" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_90bc5469-e3d7-4660-be70-ab3375bd4a80" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e54fa48f-7ee8-4ef4-944e-3ca026f77e68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_e54fa48f-7ee8-4ef4-944e-3ca026f77e68_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e54fa48f-7ee8-4ef4-944e-3ca026f77e68" xlink:to="loc_us-gaap_RelatedPartyDomain_e54fa48f-7ee8-4ef4-944e-3ca026f77e68_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_95e08503-97bb-4e6e-83fb-d1ff29bda150" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_e54fa48f-7ee8-4ef4-944e-3ca026f77e68" xlink:to="loc_us-gaap_RelatedPartyDomain_95e08503-97bb-4e6e-83fb-d1ff29bda150" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_9c856373-454c-4a10-aa7d-f85a12666191" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_95e08503-97bb-4e6e-83fb-d1ff29bda150" xlink:to="loc_srt_AffiliatedEntityMember_9c856373-454c-4a10-aa7d-f85a12666191" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_079738be-1b2c-4611-a26d-7d439bdb30a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e21af108-e2ac-45ad-8c0a-e3eaa0edcc6d" xlink:to="loc_us-gaap_InterestExpense_079738be-1b2c-4611-a26d-7d439bdb30a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingInterestExpense_084306e3-d3cd-4bf7-8bcf-42645834da42" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e21af108-e2ac-45ad-8c0a-e3eaa0edcc6d" xlink:to="loc_us-gaap_FinancingInterestExpense_084306e3-d3cd-4bf7-8bcf-42645834da42" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OrganizationandBasisofPresentationNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OrganizationandBasisofPresentationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OrganizationandBasisofPresentationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductInformationLineItems_0f5b13ff-2e0d-4aeb-8dcc-9ff50c419449" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProductInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_f4e4b74c-65d2-4681-ac38-115d8792bf51" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductInformationLineItems_0f5b13ff-2e0d-4aeb-8dcc-9ff50c419449" xlink:to="loc_us-gaap_MinorityInterestTable_f4e4b74c-65d2-4681-ac38-115d8792bf51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_b21211a1-fc0f-4689-b901-208be15f4d72" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_f4e4b74c-65d2-4681-ac38-115d8792bf51" xlink:to="loc_srt_StatementGeographicalAxis_b21211a1-fc0f-4689-b901-208be15f4d72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_b21211a1-fc0f-4689-b901-208be15f4d72_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_b21211a1-fc0f-4689-b901-208be15f4d72" xlink:to="loc_srt_SegmentGeographicalDomain_b21211a1-fc0f-4689-b901-208be15f4d72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_62ae25c7-dd61-42ff-a310-84c2a22cf6fb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_b21211a1-fc0f-4689-b901-208be15f4d72" xlink:to="loc_srt_SegmentGeographicalDomain_62ae25c7-dd61-42ff-a310-84c2a22cf6fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_IN_930fa698-7af7-4f74-b9ac-4898850bc19d" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_IN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_62ae25c7-dd61-42ff-a310-84c2a22cf6fb" xlink:to="loc_country_IN_930fa698-7af7-4f74-b9ac-4898850bc19d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_PH_7eb997fe-387e-4a9d-85c4-6aef52677e82" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_PH"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_62ae25c7-dd61-42ff-a310-84c2a22cf6fb" xlink:to="loc_country_PH_7eb997fe-387e-4a9d-85c4-6aef52677e82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_5ba81874-a06e-4725-a6a1-121b6c006afc" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_f4e4b74c-65d2-4681-ac38-115d8792bf51" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_5ba81874-a06e-4725-a6a1-121b6c006afc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_5ba81874-a06e-4725-a6a1-121b6c006afc_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_5ba81874-a06e-4725-a6a1-121b6c006afc" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_5ba81874-a06e-4725-a6a1-121b6c006afc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_685f05c8-9cfd-435a-821c-70d0f7b62a56" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_5ba81874-a06e-4725-a6a1-121b6c006afc" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_685f05c8-9cfd-435a-821c-70d0f7b62a56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVCanopyHoldCoILLCMember_52289191-6900-4af3-a20a-c01b3ea2424b" xlink:href="onit-20240930.xsd#onit_MAVCanopyHoldCoILLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_685f05c8-9cfd-435a-821c-70d0f7b62a56" xlink:to="loc_onit_MAVCanopyHoldCoILLCMember_52289191-6900-4af3-a20a-c01b3ea2424b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_8b04c04a-290c-4d51-93b1-7fcaace1c622" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductInformationLineItems_0f5b13ff-2e0d-4aeb-8dcc-9ff50c419449" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_8b04c04a-290c-4d51-93b1-7fcaace1c622" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityNumberOfEmployees_23f33969-6af8-4b10-9f2b-b1a1e8041a7f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityNumberOfEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductInformationLineItems_0f5b13ff-2e0d-4aeb-8dcc-9ff50c419449" xlink:to="loc_dei_EntityNumberOfEmployees_23f33969-6af8-4b10-9f2b-b1a1e8041a7f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_c1cddaf5-fde6-47b3-a1de-764d673dbe4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_c1cddaf5-fde6-47b3-a1de-764d673dbe4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_c1cddaf5-fde6-47b3-a1de-764d673dbe4c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_c1cddaf5-fde6-47b3-a1de-764d673dbe4c" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_c1cddaf5-fde6-47b3-a1de-764d673dbe4c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_cdb29561-5dec-48de-af64-1db2f4cb6870" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_c1cddaf5-fde6-47b3-a1de-764d673dbe4c" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_cdb29561-5dec-48de-af64-1db2f4cb6870" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GinnieMaeLoansMember_b2b4098c-fbf8-4417-80ec-96936fe362f2" xlink:href="onit-20240930.xsd#onit_GinnieMaeLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_cdb29561-5dec-48de-af64-1db2f4cb6870" xlink:to="loc_onit_GinnieMaeLoansMember_b2b4098c-fbf8-4417-80ec-96936fe362f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:to="loc_us-gaap_CreditFacilityAxis_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7" xlink:to="loc_us-gaap_CreditFacilityDomain_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_6cb037cb-361a-4c31-908a-fabfb29465d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_bddfc4bf-96ea-4bd9-a3dd-cf161f72a7c7" xlink:to="loc_us-gaap_CreditFacilityDomain_6cb037cb-361a-4c31-908a-fabfb29465d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageWarehouseAgreementMember_ec362521-db82-4501-98cc-2bff71f10f73" xlink:href="onit-20240930.xsd#onit_MortgageWarehouseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_6cb037cb-361a-4c31-908a-fabfb29465d5" xlink:to="loc_onit_MortgageWarehouseAgreementMember_ec362521-db82-4501-98cc-2bff71f10f73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_WarehouseMortgageLoanFinancingFacilityMember_8c798141-5a1b-411c-9943-abebb515dc82" xlink:href="onit-20240930.xsd#onit_WarehouseMortgageLoanFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_6cb037cb-361a-4c31-908a-fabfb29465d5" xlink:to="loc_onit_WarehouseMortgageLoanFinancingFacilityMember_8c798141-5a1b-411c-9943-abebb515dc82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_4c327ea7-859e-4d92-bd93-af9649a47194" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:to="loc_us-gaap_DebtInstrumentAxis_4c327ea7-859e-4d92-bd93-af9649a47194" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4c327ea7-859e-4d92-bd93-af9649a47194_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_4c327ea7-859e-4d92-bd93-af9649a47194" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4c327ea7-859e-4d92-bd93-af9649a47194_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_cfce88d6-f7c4-488e-987b-f19dd051a159" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_4c327ea7-859e-4d92-bd93-af9649a47194" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_cfce88d6-f7c4-488e-987b-f19dd051a159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_d074f77c-0ba5-4897-bf61-be2ca1850d99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_cfce88d6-f7c4-488e-987b-f19dd051a159" xlink:to="loc_us-gaap_SecuredDebtMember_d074f77c-0ba5-4897-bf61-be2ca1850d99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_b06ab085-683f-4227-9155-7aa99d409f3b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_b3fcc70a-a578-4e99-8c8e-8f804fd19e27" xlink:to="loc_srt_ConsolidatedEntitiesAxis_b06ab085-683f-4227-9155-7aa99d409f3b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_b06ab085-683f-4227-9155-7aa99d409f3b_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_b06ab085-683f-4227-9155-7aa99d409f3b" xlink:to="loc_srt_ConsolidatedEntitiesDomain_b06ab085-683f-4227-9155-7aa99d409f3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_6d75cd23-0402-47fa-888e-58103286f1f3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_b06ab085-683f-4227-9155-7aa99d409f3b" xlink:to="loc_srt_ConsolidatedEntitiesDomain_6d75cd23-0402-47fa-888e-58103286f1f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_2008f133-611c-41c8-8b31-86a611f2d699" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_6d75cd23-0402-47fa-888e-58103286f1f3" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_2008f133-611c-41c8-8b31-86a611f2d699" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AveragePeriodtoSecuritization_8bcae462-adbd-4ca5-92d3-16c4f1ab952b" xlink:href="onit-20240930.xsd#onit_AveragePeriodtoSecuritization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_onit_AveragePeriodtoSecuritization_8bcae462-adbd-4ca5-92d3-16c4f1ab952b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales_15c5865a-c0be-4438-81f7-3baeb5af1d41" xlink:href="onit-20240930.xsd#onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales_15c5865a-c0be-4438-81f7-3baeb5af1d41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PercentageOfLoanTransferredThroughSecuritizationSixtyDaysOrMorePastDue_1aa0befe-5bf2-456d-8199-97e5551d853b" xlink:href="onit-20240930.xsd#onit_PercentageOfLoanTransferredThroughSecuritizationSixtyDaysOrMorePastDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_onit_PercentageOfLoanTransferredThroughSecuritizationSixtyDaysOrMorePastDue_1aa0befe-5bf2-456d-8199-97e5551d853b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableThresholdPeriodPastDue_89ef3847-76a8-4534-8021-ace1a6b1bed4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableThresholdPeriodPastDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_us-gaap_FinancingReceivableThresholdPeriodPastDue_89ef3847-76a8-4534-8021-ace1a6b1bed4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepositLiabilitiesCollateralIssuedFinancialInstruments_f6a524b7-2faf-40eb-b3d5-aa026abef7a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepositLiabilitiesCollateralIssuedFinancialInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_us-gaap_DepositLiabilitiesCollateralIssuedFinancialInstruments_f6a524b7-2faf-40eb-b3d5-aa026abef7a7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_7a2f9c58-e557-466c-87c5-667a67ddd129" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgagesHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_c3637467-ad9d-471a-891a-398d068a7ea8" xlink:to="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_7a2f9c58-e557-466c-87c5-667a67ddd129" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleofAssetsThatRelatetoContinuingInvolvementwithTransferredFinancialAssetswithServicingRightsandMaximumExposuretoLossIncludingtheUnpaidPrincipalBalanceDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesScheduleofAssetsThatRelatetoContinuingInvolvementwithTransferredFinancialAssetswithServicingRightsandMaximumExposuretoLossIncludingtheUnpaidPrincipalBalanceDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleofAssetsThatRelatetoContinuingInvolvementwithTransferredFinancialAssetswithServicingRightsandMaximumExposuretoLossIncludingtheUnpaidPrincipalBalanceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_7ad64d28-b8e0-4aa6-92f8-420a65626ef3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_a19bbba6-9ce2-4d5c-833b-5f1a91cd1ea2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_7ad64d28-b8e0-4aa6-92f8-420a65626ef3" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_a19bbba6-9ce2-4d5c-833b-5f1a91cd1ea2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_af3f6288-d515-4b1f-a00c-e5013e172918" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_a19bbba6-9ce2-4d5c-833b-5f1a91cd1ea2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_af3f6288-d515-4b1f-a00c-e5013e172918" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_af3f6288-d515-4b1f-a00c-e5013e172918_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_af3f6288-d515-4b1f-a00c-e5013e172918" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_af3f6288-d515-4b1f-a00c-e5013e172918_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b741b4c6-11e5-4de0-acf4-2491327edee3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_af3f6288-d515-4b1f-a00c-e5013e172918" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b741b4c6-11e5-4de0-acf4-2491327edee3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMortgageServicingRightsMember_bc55a5f9-9f35-4d02-a744-f40ac37657c6" xlink:href="onit-20240930.xsd#onit_FairValueMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b741b4c6-11e5-4de0-acf4-2491327edee3" xlink:to="loc_onit_FairValueMortgageServicingRightsMember_bc55a5f9-9f35-4d02-a744-f40ac37657c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesAndMatchFundedAdvancesMember_e904ecf1-8509-4d44-9b27-eea8754323fe" xlink:href="onit-20240930.xsd#onit_AdvancesAndMatchFundedAdvancesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b741b4c6-11e5-4de0-acf4-2491327edee3" xlink:to="loc_onit_AdvancesAndMatchFundedAdvancesMember_e904ecf1-8509-4d44-9b27-eea8754323fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatoryAgencyAxis_f713d01c-4ebc-4585-8400-25f663de4c2b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RegulatoryAgencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_a19bbba6-9ce2-4d5c-833b-5f1a91cd1ea2" xlink:to="loc_us-gaap_RegulatoryAgencyAxis_f713d01c-4ebc-4585-8400-25f663de4c2b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatoryAgencyDomain_f713d01c-4ebc-4585-8400-25f663de4c2b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RegulatoryAgencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RegulatoryAgencyAxis_f713d01c-4ebc-4585-8400-25f663de4c2b" xlink:to="loc_us-gaap_RegulatoryAgencyDomain_f713d01c-4ebc-4585-8400-25f663de4c2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatoryAgencyDomain_5d3b6056-92d1-4131-bb95-d05eed8b542f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RegulatoryAgencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RegulatoryAgencyAxis_f713d01c-4ebc-4585-8400-25f663de4c2b" xlink:to="loc_us-gaap_RegulatoryAgencyDomain_5d3b6056-92d1-4131-bb95-d05eed8b542f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GinnieMaeMember_95252be9-b25e-4a57-96c7-19e9421d00d7" xlink:href="onit-20240930.xsd#onit_GinnieMaeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RegulatoryAgencyDomain_5d3b6056-92d1-4131-bb95-d05eed8b542f" xlink:to="loc_onit_GinnieMaeMember_95252be9-b25e-4a57-96c7-19e9421d00d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestsContinuedToBeHeldByTransferorFairValue_49185f2f-8ebb-4c86-bd16-a8d174d943f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestsContinuedToBeHeldByTransferorFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_7ad64d28-b8e0-4aa6-92f8-420a65626ef3" xlink:to="loc_us-gaap_InterestsContinuedToBeHeldByTransferorFairValue_49185f2f-8ebb-4c86-bd16-a8d174d943f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnpaidPrincipalBalanceOfLoansTransferred_b92a0367-5058-4ae4-9943-aeba139af0a8" xlink:href="onit-20240930.xsd#onit_UnpaidPrincipalBalanceOfLoansTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_7ad64d28-b8e0-4aa6-92f8-420a65626ef3" xlink:to="loc_onit_UnpaidPrincipalBalanceOfLoansTransferred_b92a0367-5058-4ae4-9943-aeba139af0a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MaximumExposureToLoss_3c629b88-cb9a-4a7c-9291-d752a189ffa7" xlink:href="onit-20240930.xsd#onit_MaximumExposureToLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_7ad64d28-b8e0-4aa6-92f8-420a65626ef3" xlink:to="loc_onit_MaximumExposureToLoss_3c629b88-cb9a-4a7c-9291-d752a189ffa7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfSecuritizationReverseMortgageLoansBuyoutsAndFinancingLiabilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesScheduleOfSecuritizationReverseMortgageLoansBuyoutsAndFinancingLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfSecuritizationReverseMortgageLoansBuyoutsAndFinancingLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_6595e274-493b-4f2d-b9c1-02e9991ff3ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_6595e274-493b-4f2d-b9c1-02e9991ff3ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_99b2e8dd-cd2d-40a7-b18e-95f0651f222f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_6595e274-493b-4f2d-b9c1-02e9991ff3ac" xlink:to="loc_srt_ConsolidatedEntitiesAxis_99b2e8dd-cd2d-40a7-b18e-95f0651f222f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_99b2e8dd-cd2d-40a7-b18e-95f0651f222f_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_99b2e8dd-cd2d-40a7-b18e-95f0651f222f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_99b2e8dd-cd2d-40a7-b18e-95f0651f222f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_ec496cf4-1b14-4c49-82f0-535109851ecd" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_99b2e8dd-cd2d-40a7-b18e-95f0651f222f" xlink:to="loc_srt_ConsolidatedEntitiesDomain_ec496cf4-1b14-4c49-82f0-535109851ecd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_50e0042e-c512-41e9-92c9-566ca39575db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_ec496cf4-1b14-4c49-82f0-535109851ecd" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_50e0042e-c512-41e9-92c9-566ca39575db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_29cb30da-fea2-4660-a590-e2db48cc6ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_6595e274-493b-4f2d-b9c1-02e9991ff3ac" xlink:to="loc_us-gaap_CreditFacilityAxis_29cb30da-fea2-4660-a590-e2db48cc6ac2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_29cb30da-fea2-4660-a590-e2db48cc6ac2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_29cb30da-fea2-4660-a590-e2db48cc6ac2" xlink:to="loc_us-gaap_CreditFacilityDomain_29cb30da-fea2-4660-a590-e2db48cc6ac2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_7814c0c2-0d11-46e6-bdbe-c76df378b33f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_29cb30da-fea2-4660-a590-e2db48cc6ac2" xlink:to="loc_us-gaap_CreditFacilityDomain_7814c0c2-0d11-46e6-bdbe-c76df378b33f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_WarehouseMortgageLoanFinancingFacilityMember_5ee5444c-48c4-406c-b54e-189ef49e0657" xlink:href="onit-20240930.xsd#onit_WarehouseMortgageLoanFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7814c0c2-0d11-46e6-bdbe-c76df378b33f" xlink:to="loc_onit_WarehouseMortgageLoanFinancingFacilityMember_5ee5444c-48c4-406c-b54e-189ef49e0657" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageWarehouseAgreementMember_9e7a00bc-949f-416f-a507-c4a742c90cbe" xlink:href="onit-20240930.xsd#onit_MortgageWarehouseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7814c0c2-0d11-46e6-bdbe-c76df378b33f" xlink:to="loc_onit_MortgageWarehouseAgreementMember_9e7a00bc-949f-416f-a507-c4a742c90cbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_f42e6d25-4a55-4735-9c50-e31d908ac2a0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgagesHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_f42e6d25-4a55-4735-9c50-e31d908ac2a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_9ccca652-f335-4104-811c-021822335d53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_OtherReceivables_9ccca652-f335-4104-811c-021822335d53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RealEstateOwned_4f103456-5019-4f0c-a165-6b5f52214f02" xlink:href="onit-20240930.xsd#onit_RealEstateOwned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_onit_RealEstateOwned_4f103456-5019-4f0c-a165-6b5f52214f02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtServiceAccounts_6f18f21d-17c9-4d1f-b77a-3650bf01b55f" xlink:href="onit-20240930.xsd#onit_DebtServiceAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_onit_DebtServiceAccounts_6f18f21d-17c9-4d1f-b77a-3650bf01b55f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermBorrowings_da26a0d8-6cf4-45b2-aaa7-cc82aea33fa1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_OtherShortTermBorrowings_da26a0d8-6cf4-45b2-aaa7-cc82aea33fa1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_9d827d70-806a-4b44-975a-7d65845eddd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_9d827d70-806a-4b44-975a-7d65845eddd9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_6d18fa63-7bbb-4ef7-b130-34bcd7d86a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_6d18fa63-7bbb-4ef7-b130-34bcd7d86a6b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_1e20ec48-59ce-4288-86bc-7cfff3d1b8ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_Liabilities_1e20ec48-59ce-4288-86bc-7cfff3d1b8ec" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_4ae31550-24f9-4049-b649-093c57ac164e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_RestrictedCash_4ae31550-24f9-4049-b649-093c57ac164e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_fa04ae27-7b76-4cb5-845f-98301a2a3a67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_21f7e48a-d1aa-434e-a3c6-ed232a457763" xlink:to="loc_us-gaap_Assets_fa04ae27-7b76-4cb5-845f-98301a2a3a67" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAdvanceFinancingFacilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAdvanceFinancingFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAdvanceFinancingFacilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_d888d350-9dd5-4dc6-87d4-7b598dfd39dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_8005f8f1-333a-4f97-aca1-8e828b4f0db3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_d888d350-9dd5-4dc6-87d4-7b598dfd39dd" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_8005f8f1-333a-4f97-aca1-8e828b4f0db3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_2e18ff3b-2ae0-4383-b149-2b7ffe221c50" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_8005f8f1-333a-4f97-aca1-8e828b4f0db3" xlink:to="loc_srt_ConsolidatedEntitiesAxis_2e18ff3b-2ae0-4383-b149-2b7ffe221c50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_2e18ff3b-2ae0-4383-b149-2b7ffe221c50_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_2e18ff3b-2ae0-4383-b149-2b7ffe221c50" xlink:to="loc_srt_ConsolidatedEntitiesDomain_2e18ff3b-2ae0-4383-b149-2b7ffe221c50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_90263d00-ccfc-4faa-ae10-bd393b35e576" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_2e18ff3b-2ae0-4383-b149-2b7ffe221c50" xlink:to="loc_srt_ConsolidatedEntitiesDomain_90263d00-ccfc-4faa-ae10-bd393b35e576" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_07abad1d-ada7-4bbe-a172-f538801cc98d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_90263d00-ccfc-4faa-ae10-bd393b35e576" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_07abad1d-ada7-4bbe-a172-f538801cc98d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_a2de0104-c2a5-4a2b-b3cf-f39707bf2035" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_8005f8f1-333a-4f97-aca1-8e828b4f0db3" xlink:to="loc_us-gaap_CreditFacilityAxis_a2de0104-c2a5-4a2b-b3cf-f39707bf2035" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_a2de0104-c2a5-4a2b-b3cf-f39707bf2035_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_a2de0104-c2a5-4a2b-b3cf-f39707bf2035" xlink:to="loc_us-gaap_CreditFacilityDomain_a2de0104-c2a5-4a2b-b3cf-f39707bf2035_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_f4fd6320-203b-4712-bb2d-6f021cbf1485" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_a2de0104-c2a5-4a2b-b3cf-f39707bf2035" xlink:to="loc_us-gaap_CreditFacilityDomain_f4fd6320-203b-4712-bb2d-6f021cbf1485" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MatchFundedLiabiltiesMember_42552f17-38e8-4d94-a6d0-0127462d4e7c" xlink:href="onit-20240930.xsd#onit_MatchFundedLiabiltiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_f4fd6320-203b-4712-bb2d-6f021cbf1485" xlink:to="loc_onit_MatchFundedLiabiltiesMember_42552f17-38e8-4d94-a6d0-0127462d4e7c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssetsCarryingAmount_83cfeb0d-8f6e-4dd9-9d98-74c62e7c67d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAccountedForAsSecuredBorrowingsAssetsCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_d888d350-9dd5-4dc6-87d4-7b598dfd39dd" xlink:to="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssetsCarryingAmount_83cfeb0d-8f6e-4dd9-9d98-74c62e7c67d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtServiceAccounts_e29ba1d7-9339-425d-b084-69224428b91d" xlink:href="onit-20240930.xsd#onit_DebtServiceAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_d888d350-9dd5-4dc6-87d4-7b598dfd39dd" xlink:to="loc_onit_DebtServiceAccounts_e29ba1d7-9339-425d-b084-69224428b91d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_4e22a655-0884-4be6-a9b1-0e4daf6edba8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_d888d350-9dd5-4dc6-87d4-7b598dfd39dd" xlink:to="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_4e22a655-0884-4be6-a9b1-0e4daf6edba8" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAgencyMSRFinancingFacilityDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAgencyMSRFinancingFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesScheduleOfCarryingValueandClassificationofAssetsandLiabilitiesofAgencyMSRFinancingFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_e9fb3f43-caa0-49b5-b62a-93cde341cec0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_fdf926a8-c036-4a10-8cc0-a1acd1d62b77" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_e9fb3f43-caa0-49b5-b62a-93cde341cec0" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_fdf926a8-c036-4a10-8cc0-a1acd1d62b77" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_ca4f5445-cf13-41e0-98b5-98f39a8fad19" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_fdf926a8-c036-4a10-8cc0-a1acd1d62b77" xlink:to="loc_srt_ConsolidatedEntitiesAxis_ca4f5445-cf13-41e0-98b5-98f39a8fad19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_ca4f5445-cf13-41e0-98b5-98f39a8fad19_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_ca4f5445-cf13-41e0-98b5-98f39a8fad19" xlink:to="loc_srt_ConsolidatedEntitiesDomain_ca4f5445-cf13-41e0-98b5-98f39a8fad19_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_f745bfca-75e0-4f43-8b5a-1ddf7aaf28ac" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_ca4f5445-cf13-41e0-98b5-98f39a8fad19" xlink:to="loc_srt_ConsolidatedEntitiesDomain_f745bfca-75e0-4f43-8b5a-1ddf7aaf28ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_b70a4fe8-ae09-4732-ad58-819767b666a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_f745bfca-75e0-4f43-8b5a-1ddf7aaf28ac" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_b70a4fe8-ae09-4732-ad58-819767b666a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e962e6c0-db56-4bc4-acf0-af51b829ccf0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_fdf926a8-c036-4a10-8cc0-a1acd1d62b77" xlink:to="loc_us-gaap_DebtInstrumentAxis_e962e6c0-db56-4bc4-acf0-af51b829ccf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e962e6c0-db56-4bc4-acf0-af51b829ccf0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e962e6c0-db56-4bc4-acf0-af51b829ccf0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e962e6c0-db56-4bc4-acf0-af51b829ccf0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_077dafd9-d6d8-4c25-8447-88bf27061554" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e962e6c0-db56-4bc4-acf0-af51b829ccf0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_077dafd9-d6d8-4c25-8447-88bf27061554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_93a3d28a-df5e-47fa-b843-2b51b6a9d909" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_077dafd9-d6d8-4c25-8447-88bf27061554" xlink:to="loc_us-gaap_SecuredDebtMember_93a3d28a-df5e-47fa-b843-2b51b6a9d909" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_61bc7f8c-ed03-41df-a4d6-45e064ceea8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_e9fb3f43-caa0-49b5-b62a-93cde341cec0" xlink:to="loc_us-gaap_ServicingAsset_61bc7f8c-ed03-41df-a4d6-45e064ceea8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtServiceAccounts_64e9e81e-f95d-44f3-bc6a-22686b60d872" xlink:href="onit-20240930.xsd#onit_DebtServiceAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_e9fb3f43-caa0-49b5-b62a-93cde341cec0" xlink:to="loc_onit_DebtServiceAccounts_64e9e81e-f95d-44f3-bc6a-22686b60d872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_2c1df425-c431-44b3-b55b-1cfc1c24920c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_e9fb3f43-caa0-49b5-b62a-93cde341cec0" xlink:to="loc_us-gaap_ShortTermBorrowings_2c1df425-c431-44b3-b55b-1cfc1c24920c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesCarryingValueandClassificationofAssetsAndLiabilitiesofPLSNotesFacilityDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SecuritizationsandVariableInterestEntitiesCarryingValueandClassificationofAssetsAndLiabilitiesofPLSNotesFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SecuritizationsandVariableInterestEntitiesCarryingValueandClassificationofAssetsAndLiabilitiesofPLSNotesFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_34baae6a-193c-403c-b021-1ce148f74ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:to="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_34baae6a-193c-403c-b021-1ce148f74ffa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_00275fa6-b5c5-420f-8f82-24eeea4902be" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_34baae6a-193c-403c-b021-1ce148f74ffa" xlink:to="loc_srt_ConsolidatedEntitiesAxis_00275fa6-b5c5-420f-8f82-24eeea4902be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_00275fa6-b5c5-420f-8f82-24eeea4902be_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_00275fa6-b5c5-420f-8f82-24eeea4902be" xlink:to="loc_srt_ConsolidatedEntitiesDomain_00275fa6-b5c5-420f-8f82-24eeea4902be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_aecde140-5a6a-4d7b-991a-d8ca5dd6f606" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_00275fa6-b5c5-420f-8f82-24eeea4902be" xlink:to="loc_srt_ConsolidatedEntitiesDomain_aecde140-5a6a-4d7b-991a-d8ca5dd6f606" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_27277413-9ec9-41ce-99a2-40307288f138" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_aecde140-5a6a-4d7b-991a-d8ca5dd6f606" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_27277413-9ec9-41ce-99a2-40307288f138" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e2f71f16-337f-43f0-bfe0-600c4fc14034" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_34baae6a-193c-403c-b021-1ce148f74ffa" xlink:to="loc_us-gaap_DebtInstrumentAxis_e2f71f16-337f-43f0-bfe0-600c4fc14034" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e2f71f16-337f-43f0-bfe0-600c4fc14034_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e2f71f16-337f-43f0-bfe0-600c4fc14034" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e2f71f16-337f-43f0-bfe0-600c4fc14034_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_aa41da84-4bae-4d79-ac6e-21708b98ca83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e2f71f16-337f-43f0-bfe0-600c4fc14034" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_aa41da84-4bae-4d79-ac6e-21708b98ca83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_f0b46dab-89d7-4882-83c1-ad84d5eab394" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_aa41da84-4bae-4d79-ac6e-21708b98ca83" xlink:to="loc_us-gaap_SecuredDebtMember_f0b46dab-89d7-4882-83c1-ad84d5eab394" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_d196b795-f440-48cd-a365-777b9ff4228b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTable_34baae6a-193c-403c-b021-1ce148f74ffa" xlink:to="loc_us-gaap_CreditFacilityAxis_d196b795-f440-48cd-a365-777b9ff4228b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_d196b795-f440-48cd-a365-777b9ff4228b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_d196b795-f440-48cd-a365-777b9ff4228b" xlink:to="loc_us-gaap_CreditFacilityDomain_d196b795-f440-48cd-a365-777b9ff4228b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c4bf5ffa-9e48-40dd-8966-86fc368daf60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_d196b795-f440-48cd-a365-777b9ff4228b" xlink:to="loc_us-gaap_CreditFacilityDomain_c4bf5ffa-9e48-40dd-8966-86fc368daf60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AgencyAndPLSMortgageServicingRightsFinancingFacilityMember_86485252-5bb1-445c-ad29-b472ba1f9ab3" xlink:href="onit-20240930.xsd#onit_AgencyAndPLSMortgageServicingRightsFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_c4bf5ffa-9e48-40dd-8966-86fc368daf60" xlink:to="loc_onit_AgencyAndPLSMortgageServicingRightsFinancingFacilityMember_86485252-5bb1-445c-ad29-b472ba1f9ab3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_bb7bfeca-3d1a-432c-aa0c-96f5c7fa3137" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:to="loc_us-gaap_ServicingAsset_bb7bfeca-3d1a-432c-aa0c-96f5c7fa3137" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtServiceAccounts_795f7b6f-5274-4ceb-b11b-1f53a64336f8" xlink:href="onit-20240930.xsd#onit_DebtServiceAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:to="loc_onit_DebtServiceAccounts_795f7b6f-5274-4ceb-b11b-1f53a64336f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_62f469aa-9a7d-4c92-a5f6-210df2adc1c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:to="loc_us-gaap_ShortTermBorrowings_62f469aa-9a7d-4c92-a5f6-210df2adc1c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_b32e6683-d0fd-416c-ab08-8fa0c9390fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementLineItems_6189bdb6-a34d-431f-87ec-227d9090898e" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_b32e6683-d0fd-416c-ab08-8fa0c9390fe9" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/FairValueScheduleofFairValueAssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#FairValueScheduleofFairValueAssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/FairValueScheduleofFairValueAssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ed363f61-e574-42ae-8823-082cdcfb38ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ed363f61-e574-42ae-8823-082cdcfb38ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_ed363f61-e574-42ae-8823-082cdcfb38ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ed363f61-e574-42ae-8823-082cdcfb38ae" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_ed363f61-e574-42ae-8823-082cdcfb38ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aa39898-aa89-4eb5-ae26-a483af682a32" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_ed363f61-e574-42ae-8823-082cdcfb38ae" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aa39898-aa89-4eb5-ae26-a483af682a32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_7be38ef7-d3bc-46c5-b8e6-7496cfcc3144" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aa39898-aa89-4eb5-ae26-a483af682a32" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_7be38ef7-d3bc-46c5-b8e6-7496cfcc3144" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_f6fcf6df-4607-41af-98d2-124dbf2ea092" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aa39898-aa89-4eb5-ae26-a483af682a32" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_f6fcf6df-4607-41af-98d2-124dbf2ea092" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_84a376a5-43de-4f8f-ae18-4bd93dda1be5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0aa39898-aa89-4eb5-ae26-a483af682a32" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_84a376a5-43de-4f8f-ae18-4bd93dda1be5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_220177dd-3656-464d-9ca7-b2a3ccbf5112" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_FinancialInstrumentAxis_220177dd-3656-464d-9ca7-b2a3ccbf5112" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_220177dd-3656-464d-9ca7-b2a3ccbf5112_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_220177dd-3656-464d-9ca7-b2a3ccbf5112" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_220177dd-3656-464d-9ca7-b2a3ccbf5112_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a04e25f0-67fe-43a5-ba71-93b786b73248" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_220177dd-3656-464d-9ca7-b2a3ccbf5112" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a04e25f0-67fe-43a5-ba71-93b786b73248" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldforInvestmentSecuritizationTrustsMember_137d9c92-1e26-49be-a314-d5effa19fc42" xlink:href="onit-20240930.xsd#onit_LoansHeldforInvestmentSecuritizationTrustsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a04e25f0-67fe-43a5-ba71-93b786b73248" xlink:to="loc_onit_LoansHeldforInvestmentSecuritizationTrustsMember_137d9c92-1e26-49be-a314-d5effa19fc42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_8bee38a4-3825-42a9-8db9-6cb3df617308" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_8bee38a4-3825-42a9-8db9-6cb3df617308" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8bee38a4-3825-42a9-8db9-6cb3df617308_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_8bee38a4-3825-42a9-8db9-6cb3df617308" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8bee38a4-3825-42a9-8db9-6cb3df617308_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5e86e799-1776-4795-81d2-69a303aa0c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_8bee38a4-3825-42a9-8db9-6cb3df617308" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5e86e799-1776-4795-81d2-69a303aa0c6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_9fb69394-fadd-4dc2-833a-8d45a7546c2c" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5e86e799-1776-4795-81d2-69a303aa0c6d" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_9fb69394-fadd-4dc2-833a-8d45a7546c2c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_05d9c9cd-71b9-4e95-83b1-5e351ed0355a" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5e86e799-1776-4795-81d2-69a303aa0c6d" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_05d9c9cd-71b9-4e95-83b1-5e351ed0355a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForSaleFairValueMember_bfa51f84-5769-45cf-9c2d-a7502988356e" xlink:href="onit-20240930.xsd#onit_LoansHeldForSaleFairValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_5e86e799-1776-4795-81d2-69a303aa0c6d" xlink:to="loc_onit_LoansHeldForSaleFairValueMember_bfa51f84-5769-45cf-9c2d-a7502988356e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_1b9d1d16-8c64-4029-b61e-5c92bc52df32" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_1b9d1d16-8c64-4029-b61e-5c92bc52df32" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_1b9d1d16-8c64-4029-b61e-5c92bc52df32_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_1b9d1d16-8c64-4029-b61e-5c92bc52df32" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_1b9d1d16-8c64-4029-b61e-5c92bc52df32_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_1b9d1d16-8c64-4029-b61e-5c92bc52df32" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_2543a80c-86b4-4083-a6b6-47288a952aec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_us-gaap_InterestRateContractMember_2543a80c-86b4-4083-a6b6-47288a952aec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardLHFSTradesMember_ff38add9-6d0c-4aa7-b0df-21c9ddf3fc7f" xlink:href="onit-20240930.xsd#onit_ForwardLHFSTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_onit_ForwardLHFSTradesMember_ff38add9-6d0c-4aa7-b0df-21c9ddf3fc7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TBAForwardMortgageBackedSecuritiesTradesMember_20c12c71-9b43-410b-8fdb-4e282a51cc23" xlink:href="onit-20240930.xsd#onit_TBAForwardMortgageBackedSecuritiesTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_onit_TBAForwardMortgageBackedSecuritiesTradesMember_20c12c71-9b43-410b-8fdb-4e282a51cc23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_e72ea2e5-a7ee-4e9c-bb6f-a15d781fedb9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_us-gaap_InterestRateSwapMember_e72ea2e5-a7ee-4e9c-bb6f-a15d781fedb9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_ed4ef576-752c-4b49-81a7-502c322aa03d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_us-gaap_DerivativeMember_ed4ef576-752c-4b49-81a7-502c322aa03d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TBAForwardPipelinesTradesMember_827c0406-0c3c-4eb3-b3d0-b345576541a0" xlink:href="onit-20240930.xsd#onit_TBAForwardPipelinesTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_3db77941-35c4-4303-8c2a-3e0a831dc45d" xlink:to="loc_onit_TBAForwardPipelinesTradesMember_827c0406-0c3c-4eb3-b3d0-b345576541a0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_d288abb0-2a4d-42be-91f1-93a0c14697e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_d288abb0-2a4d-42be-91f1-93a0c14697e7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d288abb0-2a4d-42be-91f1-93a0c14697e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_d288abb0-2a4d-42be-91f1-93a0c14697e7" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_d288abb0-2a4d-42be-91f1-93a0c14697e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6f85707d-de6d-401b-881d-babfbc2b87da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_d288abb0-2a4d-42be-91f1-93a0c14697e7" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6f85707d-de6d-401b-881d-babfbc2b87da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_9dc102d0-da81-489a-95bc-a20729114b10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6f85707d-de6d-401b-881d-babfbc2b87da" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_9dc102d0-da81-489a-95bc-a20729114b10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_f63a178a-fc21-4cea-8175-536082035c02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6f85707d-de6d-401b-881d-babfbc2b87da" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_f63a178a-fc21-4cea-8175-536082035c02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_704f2063-736f-4123-9d3f-a19a6d3a1dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_6f85707d-de6d-401b-881d-babfbc2b87da" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_704f2063-736f-4123-9d3f-a19a6d3a1dc1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryAxis_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_LienCategoryAxis_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LienCategoryAxis_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0" xlink:to="loc_us-gaap_LienCategoryDomain_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_edcbb0a1-ab27-4fe6-846a-17ddcba06fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LienCategoryAxis_e6e921d0-81a1-4ea3-8024-a1fd9e2104a0" xlink:to="loc_us-gaap_LienCategoryDomain_edcbb0a1-ab27-4fe6-846a-17ddcba06fe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JuniorLienMember_c0b1a1d0-aaa1-4f02-91b1-89c82b8afac0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_JuniorLienMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_edcbb0a1-ab27-4fe6-846a-17ddcba06fe9" xlink:to="loc_us-gaap_JuniorLienMember_c0b1a1d0-aaa1-4f02-91b1-89c82b8afac0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_7ada43b3-59a9-4fa3-b180-310f6ead171d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_1901289a-0859-40d7-859c-6535772dcce0" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_7ada43b3-59a9-4fa3-b180-310f6ead171d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_7ada43b3-59a9-4fa3-b180-310f6ead171d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_7ada43b3-59a9-4fa3-b180-310f6ead171d" xlink:to="loc_us-gaap_ReceivableTypeDomain_7ada43b3-59a9-4fa3-b180-310f6ead171d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_29f2cacb-db3f-4a8c-8d87-f6a97c1186b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_7ada43b3-59a9-4fa3-b180-310f6ead171d" xlink:to="loc_us-gaap_ReceivableTypeDomain_29f2cacb-db3f-4a8c-8d87-f6a97c1186b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GinnieMaeLoansMember_1d6f6f68-dce0-45ea-9b27-1d816e9e272d" xlink:href="onit-20240930.xsd#onit_GinnieMaeLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_29f2cacb-db3f-4a8c-8d87-f6a97c1186b9" xlink:to="loc_onit_GinnieMaeLoansMember_1d6f6f68-dce0-45ea-9b27-1d816e9e272d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancialAssetsAbstract_df08126d-d283-4ed7-a47b-847b32eb46c5" xlink:href="onit-20240930.xsd#onit_FinancialAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_onit_FinancialAssetsAbstract_df08126d-d283-4ed7-a47b-847b32eb46c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:href="onit-20240930.xsd#onit_LoansHeldForSaleAtFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancialAssetsAbstract_df08126d-d283-4ed7-a47b-847b32eb46c5" xlink:to="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_99c74dd4-f307-4685-b52f-785f41d66ca4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_99c74dd4-f307-4685-b52f-785f41d66ca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldforInvestmentFairValueDisclosure_11ecfc75-67b5-4e55-8f39-ca34a452588b" xlink:href="onit-20240930.xsd#onit_LoansHeldforInvestmentFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:to="loc_onit_LoansHeldforInvestmentFairValueDisclosure_11ecfc75-67b5-4e55-8f39-ca34a452588b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForSaleAtLowerCostFairValueDisclosure_fd37f346-bdcb-4a7f-8919-9c0d41290c27" xlink:href="onit-20240930.xsd#onit_LoansHeldForSaleAtLowerCostFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:to="loc_onit_LoansHeldForSaleAtLowerCostFairValueDisclosure_fd37f346-bdcb-4a7f-8919-9c0d41290c27" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_a9f90696-b677-4f97-8335-9b37f7af461a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgagesHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LoansHeldForSaleAtFairValueAbstract_5acc5026-bb96-44bf-9b4b-422c86ad6cdd" xlink:to="loc_us-gaap_MortgagesHeldForSaleFairValueDisclosure_a9f90696-b677-4f97-8335-9b37f7af461a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesAndMatchFundedAdvancesFairValueDisclosure_d25a0f6b-751d-444c-a34e-acb3319a45d9" xlink:href="onit-20240930.xsd#onit_AdvancesAndMatchFundedAdvancesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancialAssetsAbstract_df08126d-d283-4ed7-a47b-847b32eb46c5" xlink:to="loc_onit_AdvancesAndMatchFundedAdvancesFairValueDisclosure_d25a0f6b-751d-444c-a34e-acb3319a45d9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesFairValueDisclosure_8ac2f270-30ed-44fd-a822-cf34bdcb4ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivablesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancialAssetsAbstract_df08126d-d283-4ed7-a47b-847b32eb46c5" xlink:to="loc_us-gaap_ReceivablesFairValueDisclosure_8ac2f270-30ed-44fd-a822-cf34bdcb4ae3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancialLiabilitiesAbstract_6193675b-7072-424c-a495-43e099b809d3" xlink:href="onit-20240930.xsd#onit_FinancialLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_onit_FinancialLiabilitiesAbstract_6193675b-7072-424c-a495-43e099b809d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_16f35703-367e-44ee-bfd9-0f572c606df6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancialLiabilitiesAbstract_6193675b-7072-424c-a495-43e099b809d3" xlink:to="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_16f35703-367e-44ee-bfd9-0f572c606df6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilitiesAbstract_5d941b4b-4efb-4f4e-b891-355c1beee67a" xlink:href="onit-20240930.xsd#onit_FinancingLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancialLiabilitiesAbstract_6193675b-7072-424c-a495-43e099b809d3" xlink:to="loc_onit_FinancingLiabilitiesAbstract_5d941b4b-4efb-4f4e-b891-355c1beee67a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecuritiesRelatedBorrowingsAtFairValue_1b08638e-e89a-44c7-90be-b2e527f23db4" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecuritiesRelatedBorrowingsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancingLiabilitiesAbstract_5d941b4b-4efb-4f4e-b891-355c1beee67a" xlink:to="loc_onit_HomeEquityConversionMortgageBackedSecuritiesRelatedBorrowingsAtFairValue_1b08638e-e89a-44c7-90be-b2e527f23db4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherFinancingLiabilities_93190022-1082-4e91-8d80-258692ed1496" xlink:href="onit-20240930.xsd#onit_OtherFinancingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_FinancingLiabilitiesAbstract_5d941b4b-4efb-4f4e-b891-355c1beee67a" xlink:to="loc_onit_OtherFinancingLiabilities_93190022-1082-4e91-8d80-258692ed1496" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract_40d3d1b0-a20b-486b-9669-5d711ec01d75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract_40d3d1b0-a20b-486b-9669-5d711ec01d75" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherShortTermBorrowings_0f8c2768-b0ab-499d-b898-45da88f73798" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract_40d3d1b0-a20b-486b-9669-5d711ec01d75" xlink:to="loc_us-gaap_OtherShortTermBorrowings_0f8c2768-b0ab-499d-b898-45da88f73798" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_29ae24d6-fc0c-4c7d-98b9-2f9d6d7de072" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuredLongtermDebtCurrentAndNoncurrentAbstract_40d3d1b0-a20b-486b-9669-5d711ec01d75" xlink:to="loc_us-gaap_LineOfCredit_29ae24d6-fc0c-4c7d-98b9-2f9d6d7de072" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_d764206c-5a2c-43f3-882a-f3f0c4255ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_d764206c-5a2c-43f3-882a-f3f0c4255ecb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_39070a7d-5795-4f20-89be-7b192ad71cbe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_d764206c-5a2c-43f3-882a-f3f0c4255ecb" xlink:to="loc_us-gaap_SecuredDebt_39070a7d-5795-4f20-89be-7b192ad71cbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_96be55ce-068f-4d02-b42f-2a34befda2f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_d764206c-5a2c-43f3-882a-f3f0c4255ecb" xlink:to="loc_us-gaap_SeniorNotes_96be55ce-068f-4d02-b42f-2a34befda2f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentDetailAbstract_04e8cce5-4daa-4ba9-97b1-95c7a6bfe2ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentDetailAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_us-gaap_DerivativeInstrumentDetailAbstract_04e8cce5-4daa-4ba9-97b1-95c7a6bfe2ce" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_f5f6eed3-b830-4968-925d-a1f033168a87" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentDetailAbstract_04e8cce5-4daa-4ba9-97b1-95c7a6bfe2ce" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_f5f6eed3-b830-4968-925d-a1f033168a87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_8098b7e1-bbd8-41f6-8124-34772d05846c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentDetailAbstract_04e8cce5-4daa-4ba9-97b1-95c7a6bfe2ce" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_8098b7e1-bbd8-41f6-8124-34772d05846c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageServiceRightsAbstract_24fdeb3b-f9c5-494c-bc7d-f0297ad63cf0" xlink:href="onit-20240930.xsd#onit_MortgageServiceRightsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_onit_MortgageServiceRightsAbstract_24fdeb3b-f9c5-494c-bc7d-f0297ad63cf0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_c7c1793d-d714-4de5-87c5-9cdf2be28207" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_MortgageServiceRightsAbstract_24fdeb3b-f9c5-494c-bc7d-f0297ad63cf0" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_c7c1793d-d714-4de5-87c5-9cdf2be28207" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_75f92e2a-0b66-4614-bf94-46ec622a6d9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_1fb5185b-6b34-4d8b-99e3-9e413ee859de" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_75f92e2a-0b66-4614-bf94-46ec622a6d9d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/FairValueScheduleofReconciliationofChangesinFairValueofLevel3AssetsandLiabilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#FairValueScheduleofReconciliationofChangesinFairValueofLevel3AssetsandLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/FairValueScheduleofReconciliationofChangesinFairValueofLevel3AssetsandLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2841d0be-af1a-4d2d-85ad-64abf657eb53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_134ca60e-7cee-4d8b-b766-a126eb78d031" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2841d0be-af1a-4d2d-85ad-64abf657eb53" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_134ca60e-7cee-4d8b-b766-a126eb78d031" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_49fde750-d329-411f-b0a7-c5314876e28c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_134ca60e-7cee-4d8b-b766-a126eb78d031" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_49fde750-d329-411f-b0a7-c5314876e28c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49fde750-d329-411f-b0a7-c5314876e28c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_49fde750-d329-411f-b0a7-c5314876e28c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_49fde750-d329-411f-b0a7-c5314876e28c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_94ebbce4-3f3f-4bb3-936c-fe316dd3c6df" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_49fde750-d329-411f-b0a7-c5314876e28c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_94ebbce4-3f3f-4bb3-936c-fe316dd3c6df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_e1d65610-9fdb-4099-89c6-eebb4e059106" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_94ebbce4-3f3f-4bb3-936c-fe316dd3c6df" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_e1d65610-9fdb-4099-89c6-eebb4e059106" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_756e742c-2438-46f3-be00-6344b9ba3828" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_134ca60e-7cee-4d8b-b766-a126eb78d031" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_756e742c-2438-46f3-be00-6344b9ba3828" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_756e742c-2438-46f3-be00-6344b9ba3828_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_756e742c-2438-46f3-be00-6344b9ba3828" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_756e742c-2438-46f3-be00-6344b9ba3828_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_569d28f8-057e-42a3-9f21-6bf293581252" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_756e742c-2438-46f3-be00-6344b9ba3828" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_569d28f8-057e-42a3-9f21-6bf293581252" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForSaleFairValueMember_8f6fa591-1da6-489b-b712-9fd627ae5656" xlink:href="onit-20240930.xsd#onit_LoansHeldForSaleFairValueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_569d28f8-057e-42a3-9f21-6bf293581252" xlink:to="loc_onit_LoansHeldForSaleFairValueMember_8f6fa591-1da6-489b-b712-9fd627ae5656" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_71c64293-3e5a-491f-bb1b-a60bbc365a32" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_569d28f8-057e-42a3-9f21-6bf293581252" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_71c64293-3e5a-491f-bb1b-a60bbc365a32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_2fc595f9-69ee-47d7-a479-1a625aa25766" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFinancialInstrumentsAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_569d28f8-057e-42a3-9f21-6bf293581252" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_2fc595f9-69ee-47d7-a479-1a625aa25766" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_a1695e30-e9f5-4984-b1b6-e0adb64529c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_134ca60e-7cee-4d8b-b766-a126eb78d031" xlink:to="loc_us-gaap_FinancialInstrumentAxis_a1695e30-e9f5-4984-b1b6-e0adb64529c2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a1695e30-e9f5-4984-b1b6-e0adb64529c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a1695e30-e9f5-4984-b1b6-e0adb64529c2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a1695e30-e9f5-4984-b1b6-e0adb64529c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7e985410-ca1f-4c7e-8ef0-a6d562c4fa7a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a1695e30-e9f5-4984-b1b6-e0adb64529c2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7e985410-ca1f-4c7e-8ef0-a6d562c4fa7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_af15b84f-b204-458a-8148-dedbb9c526d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_7e985410-ca1f-4c7e-8ef0-a6d562c4fa7a" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_af15b84f-b204-458a-8148-dedbb9c526d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c37477bc-991d-4d09-8f85-ab062394deba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2841d0be-af1a-4d2d-85ad-64abf657eb53" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c37477bc-991d-4d09-8f85-ab062394deba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_ef4e13f8-30c1-4dc2-91b0-8c1f170f49b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c37477bc-991d-4d09-8f85-ab062394deba" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_ef4e13f8-30c1-4dc2-91b0-8c1f170f49b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:href="onit-20240930.xsd#onit_PurchasesIssuancesSalesAndSettlementsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c37477bc-991d-4d09-8f85-ab062394deba" xlink:to="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_3fb81e24-f18e-4536-a851-f4a9997db275" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_3fb81e24-f18e-4536-a851-f4a9997db275" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_3a3d3918-d0f5-4a3c-ad01-4d8473fa592c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIssues_3a3d3918-d0f5-4a3c-ad01-4d8473fa592c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_a7ce7e1e-b9e8-4846-bb79-9180fc3238be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_a7ce7e1e-b9e8-4846-bb79-9180fc3238be" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_860f05d5-749f-485a-b4c5-6ddc12a23b05" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_860f05d5-749f-485a-b4c5-6ddc12a23b05" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationAssetTransfersOutOfLevel3ToLoansHeldForInvestmentAtFairValue_64fd64be-b20a-4c24-b1f0-18608eec4311" xlink:href="onit-20240930.xsd#onit_FairValueMeasurementWithUnobservableInputsReconciliationAssetTransfersOutOfLevel3ToLoansHeldForInvestmentAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationAssetTransfersOutOfLevel3ToLoansHeldForInvestmentAtFairValue_64fd64be-b20a-4c24-b1f0-18608eec4311" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToLoansHeldForSaleAtFairValue_2edc37bd-f15f-4eee-a18b-7b811ff9674c" xlink:href="onit-20240930.xsd#onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToLoansHeldForSaleAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToLoansHeldForSaleAtFairValue_2edc37bd-f15f-4eee-a18b-7b811ff9674c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToReceivablesNet_7a99c5c5-3d9c-40b8-a077-ffaf0599dc15" xlink:href="onit-20240930.xsd#onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToReceivablesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersToReceivablesNet_7a99c5c5-3d9c-40b8-a077-ffaf0599dc15" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_CapitalizationOfAdvancesOnGinnieMaeModifications_4255a9c3-df77-4dcc-b15f-a1cd04782e1b" xlink:href="onit-20240930.xsd#onit_CapitalizationOfAdvancesOnGinnieMaeModifications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_CapitalizationOfAdvancesOnGinnieMaeModifications_4255a9c3-df77-4dcc-b15f-a1cd04782e1b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisOther_30503290-f0f2-4037-9599-8228024a5e18" xlink:href="onit-20240930.xsd#onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisOther_30503290-f0f2-4037-9599-8228024a5e18" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3Other_a86b5eec-d6c4-4d34-9641-1ea2cc49c2a5" xlink:href="onit-20240930.xsd#onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3Other"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_onit_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3Other_a86b5eec-d6c4-4d34-9641-1ea2cc49c2a5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements_663b5e06-7625-4936-b030-c8b726e3a649" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_PurchasesIssuancesSalesAndSettlementsAbstract_756745fa-407c-411a-9f11-45fc9286743b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements_663b5e06-7625-4936-b030-c8b726e3a649" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalRealizedAndUnrealizedGainsAndLosses2Abstract_15b52b07-caec-4a42-9e8b-2acabe235c9d" xlink:href="onit-20240930.xsd#onit_TotalRealizedAndUnrealizedGainsAndLosses2Abstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_c37477bc-991d-4d09-8f85-ab062394deba" xlink:to="loc_onit_TotalRealizedAndUnrealizedGainsAndLosses2Abstract_15b52b07-caec-4a42-9e8b-2acabe235c9d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_2867a4d0-ef43-4217-9063-42a8356bbd23" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_TotalRealizedAndUnrealizedGainsAndLosses2Abstract_15b52b07-caec-4a42-9e8b-2acabe235c9d" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_2867a4d0-ef43-4217-9063-42a8356bbd23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_9310f572-0414-45b4-b682-deb8d5903177" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_7ed631cd-b9a3-46e1-be7e-802b8274c40a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2841d0be-af1a-4d2d-85ad-64abf657eb53" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_7ed631cd-b9a3-46e1-be7e-802b8274c40a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_5bce5545-6e04-4edc-a019-fc4d6f1b9779" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2841d0be-af1a-4d2d-85ad-64abf657eb53" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3_5bce5545-6e04-4edc-a019-fc4d6f1b9779" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/FairValueScheduleofSignificantAssumptionsusedinValuationDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#FairValueScheduleofSignificantAssumptionsusedinValuationDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/FairValueScheduleofSignificantAssumptionsusedinValuationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1cd5b127-d740-4851-bcc9-fd01574b31b2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_2ef6e9bf-961e-4772-abbd-a6e0014ca632" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1cd5b127-d740-4851-bcc9-fd01574b31b2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_2ef6e9bf-961e-4772-abbd-a6e0014ca632" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_ed1f984c-0506-4f81-b645-b09364192c18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_2ef6e9bf-961e-4772-abbd-a6e0014ca632" xlink:to="loc_us-gaap_FinancialInstrumentAxis_ed1f984c-0506-4f81-b645-b09364192c18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ed1f984c-0506-4f81-b645-b09364192c18_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ed1f984c-0506-4f81-b645-b09364192c18" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ed1f984c-0506-4f81-b645-b09364192c18_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_ed1f984c-0506-4f81-b645-b09364192c18" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldforInvestmentReverseMortgagesMember_dcfe7c0b-31eb-4f5a-9597-bf972a3f29ca" xlink:href="onit-20240930.xsd#onit_LoansHeldforInvestmentReverseMortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:to="loc_onit_LoansHeldforInvestmentReverseMortgagesMember_dcfe7c0b-31eb-4f5a-9597-bf972a3f29ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueAgencyMortgageServicingRightsMember_3627f07d-aa20-4473-a133-1a125af78174" xlink:href="onit-20240930.xsd#onit_FairValueAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:to="loc_onit_FairValueAgencyMortgageServicingRightsMember_3627f07d-aa20-4473-a133-1a125af78174" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_e1b6d717-cac0-4355-8769-d911cdc66432" xlink:href="onit-20240930.xsd#onit_FairValueNonAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:to="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_e1b6d717-cac0-4355-8769-d911cdc66432" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HMBSRelatedBorrowingsMember_1e354b11-3cf8-432f-ba24-4ec00dd745dc" xlink:href="onit-20240930.xsd#onit_HMBSRelatedBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:to="loc_onit_HMBSRelatedBorrowingsMember_1e354b11-3cf8-432f-ba24-4ec00dd745dc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageServicingRightsPledgedMember_a938cfea-f8b0-4cd1-80e4-3c983cf236fd" xlink:href="onit-20240930.xsd#onit_MortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_668020a7-ce94-4caa-a042-47568f440b38" xlink:to="loc_onit_MortgageServicingRightsPledgedMember_a938cfea-f8b0-4cd1-80e4-3c983cf236fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_decfab24-2a88-4029-9521-c46b18fee009" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_2ef6e9bf-961e-4772-abbd-a6e0014ca632" xlink:to="loc_srt_RangeAxis_decfab24-2a88-4029-9521-c46b18fee009" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_decfab24-2a88-4029-9521-c46b18fee009_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_decfab24-2a88-4029-9521-c46b18fee009" xlink:to="loc_srt_RangeMember_decfab24-2a88-4029-9521-c46b18fee009_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_aadd4b38-41e7-4d89-aec5-a61e1521d452" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_decfab24-2a88-4029-9521-c46b18fee009" xlink:to="loc_srt_RangeMember_aadd4b38-41e7-4d89-aec5-a61e1521d452" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_741fcb30-5b99-4cf9-9ab0-c06044a755d6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_aadd4b38-41e7-4d89-aec5-a61e1521d452" xlink:to="loc_srt_MinimumMember_741fcb30-5b99-4cf9-9ab0-c06044a755d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_85fff7bd-829c-4555-8cbc-7c39789726c6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_aadd4b38-41e7-4d89-aec5-a61e1521d452" xlink:to="loc_srt_MaximumMember_85fff7bd-829c-4555-8cbc-7c39789726c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_923d56cd-7f72-4c09-b97c-053cf0f88b30" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_aadd4b38-41e7-4d89-aec5-a61e1521d452" xlink:to="loc_srt_WeightedAverageMember_923d56cd-7f72-4c09-b97c-053cf0f88b30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_c3f29544-9516-491f-910c-cebb60d5d750" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_2ef6e9bf-961e-4772-abbd-a6e0014ca632" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_c3f29544-9516-491f-910c-cebb60d5d750" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_c3f29544-9516-491f-910c-cebb60d5d750_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_c3f29544-9516-491f-910c-cebb60d5d750" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_c3f29544-9516-491f-910c-cebb60d5d750_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_c3f29544-9516-491f-910c-cebb60d5d750" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember_0283036c-cafe-4036-bc8c-c03c6b1c4d8f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputExpectedTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_0283036c-cafe-4036-bc8c-c03c6b1c4d8f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPrepaymentRateMember_67d00b07-51bf-49c5-89c3-969dc6971c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputPrepaymentRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:to="loc_us-gaap_MeasurementInputPrepaymentRateMember_67d00b07-51bf-49c5-89c3-969dc6971c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_4f1d1a75-7749-4abf-8450-735f40dbc3fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_4f1d1a75-7749-4abf-8450-735f40dbc3fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDefaultRateMember_2ff7a575-e783-4b41-a95a-f567615d6b4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDefaultRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:to="loc_us-gaap_MeasurementInputDefaultRateMember_2ff7a575-e783-4b41-a95a-f567615d6b4b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MeasurementInputWeightedAverageCostToServiceMember_e56ec54c-de65-48be-8223-ba4aa9f46a46" xlink:href="onit-20240930.xsd#onit_MeasurementInputWeightedAverageCostToServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_6cc1f214-2a55-4df9-923d-1efe2dfacc3e" xlink:to="loc_onit_MeasurementInputWeightedAverageCostToServiceMember_e56ec54c-de65-48be-8223-ba4aa9f46a46" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AlternativeInvestmentMeasurementInput_dc807d3d-a9f6-42a6-9c47-a5a298933143" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestmentMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_1cd5b127-d740-4851-bcc9-fd01574b31b2" xlink:to="loc_us-gaap_AlternativeInvestmentMeasurementInput_dc807d3d-a9f6-42a6-9c47-a5a298933143" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/FairValueNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#FairValueNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/FairValueNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_82a5f337-58b0-4444-b4d1-c4f080e84c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_f361988c-70d8-48d5-8027-4d94b26b7aeb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_82a5f337-58b0-4444-b4d1-c4f080e84c9b" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_f361988c-70d8-48d5-8027-4d94b26b7aeb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_98fe23de-00e0-49ee-9778-0bbab3a0a922" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_f361988c-70d8-48d5-8027-4d94b26b7aeb" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_98fe23de-00e0-49ee-9778-0bbab3a0a922" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_98fe23de-00e0-49ee-9778-0bbab3a0a922_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_98fe23de-00e0-49ee-9778-0bbab3a0a922" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_98fe23de-00e0-49ee-9778-0bbab3a0a922_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_8b013ae4-0d73-4c41-8a63-d7cb654bade2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_98fe23de-00e0-49ee-9778-0bbab3a0a922" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_8b013ae4-0d73-4c41-8a63-d7cb654bade2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_e4d02a63-4afc-40c6-88ff-924dbfe249dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_8b013ae4-0d73-4c41-8a63-d7cb654bade2" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_e4d02a63-4afc-40c6-88ff-924dbfe249dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AlternativeInvestmentMeasurementInput_03f27f84-521a-42e0-86c4-e570862ad9c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestmentMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_82a5f337-58b0-4444-b4d1-c4f080e84c9b" xlink:to="loc_us-gaap_AlternativeInvestmentMeasurementInput_03f27f84-521a-42e0-86c4-e570862ad9c9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/LoansHeldforSaleFairValueScheduleofLoansHeldforSaleFairValueDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#LoansHeldforSaleFairValueScheduleofLoansHeldforSaleFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/LoansHeldforSaleFairValueScheduleofLoansHeldforSaleFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_65801fc2-92ad-4680-96ab-731ec891e4c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_0c010ad1-80e1-4c87-b0ca-98467f51171b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_65801fc2-92ad-4680-96ab-731ec891e4c6" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_0c010ad1-80e1-4c87-b0ca-98467f51171b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_0c010ad1-80e1-4c87-b0ca-98467f51171b" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725" xlink:to="loc_us-gaap_ReceivableTypeDomain_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6d6fc35a-e3cb-4ea4-abbc-d7a3f8386725" xlink:to="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GSELoansMember_649fd7ab-3cd7-4553-bae7-126ffa67aafc" xlink:href="onit-20240930.xsd#onit_GSELoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:to="loc_onit_GSELoansMember_649fd7ab-3cd7-4553-bae7-126ffa67aafc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GovernmentForwardLoansMember_71ca8274-e799-49b6-be65-e0411fa92db7" xlink:href="onit-20240930.xsd#onit_GovernmentForwardLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:to="loc_onit_GovernmentForwardLoansMember_71ca8274-e799-49b6-be65-e0411fa92db7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RepurchasedGinnieMaeLoansMember_ec8858fc-f863-469e-bc83-e4cc1776cf54" xlink:href="onit-20240930.xsd#onit_RepurchasedGinnieMaeLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:to="loc_onit_RepurchasedGinnieMaeLoansMember_ec8858fc-f863-469e-bc83-e4cc1776cf54" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ReverseLoansMember_e3ac4cf6-37ea-4d73-a9d6-0450e81e3284" xlink:href="onit-20240930.xsd#onit_ReverseLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:to="loc_onit_ReverseLoansMember_e3ac4cf6-37ea-4d73-a9d6-0450e81e3284" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_2276a812-9765-4df1-b2f0-bcd9b2b88546" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResidentialMortgageBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_ca0e9d91-79ff-47f3-b7db-f4517aeafb4b" xlink:to="loc_us-gaap_ResidentialMortgageBackedSecuritiesMember_2276a812-9765-4df1-b2f0-bcd9b2b88546" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_2ee3faa6-3cca-45b6-8d6c-219ddb9bcb2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_65801fc2-92ad-4680-96ab-731ec891e4c6" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_2ee3faa6-3cca-45b6-8d6c-219ddb9bcb2f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/LoansHeldforSaleFairValueScheduleofGainsonLoansHeldforSaleNetDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#LoansHeldforSaleFairValueScheduleofGainsonLoansHeldforSaleNetDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/LoansHeldforSaleFairValueScheduleofGainsonLoansHeldforSaleNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_54a98aba-43a7-4466-ab7b-402976a5c220" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_54a98aba-43a7-4466-ab7b-402976a5c220" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_54a98aba-43a7-4466-ab7b-402976a5c220" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c" xlink:to="loc_us-gaap_ReceivableTypeDomain_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_e19f33ed-9ea5-4463-96f1-5e4c31372e8c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_e87e8d1b-6f6e-49ed-95b3-c3b586cc182c" xlink:to="loc_us-gaap_ReceivableTypeDomain_e19f33ed-9ea5-4463-96f1-5e4c31372e8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardMortgageLoansMember_9f9d8e73-cbb5-4609-ba36-49f77ed625bf" xlink:href="onit-20240930.xsd#onit_ForwardMortgageLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_e19f33ed-9ea5-4463-96f1-5e4c31372e8c" xlink:to="loc_onit_ForwardMortgageLoansMember_9f9d8e73-cbb5-4609-ba36-49f77ed625bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RepurchasedGinnieMaeLoansMember_b76b5c5b-faf2-4970-b212-19c36f70db72" xlink:href="onit-20240930.xsd#onit_RepurchasedGinnieMaeLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_e19f33ed-9ea5-4463-96f1-5e4c31372e8c" xlink:to="loc_onit_RepurchasedGinnieMaeLoansMember_b76b5c5b-faf2-4970-b212-19c36f70db72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales_c3bd2d27-8e8c-4e3e-9e4e-2861b50b4625" xlink:href="onit-20240930.xsd#onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_onit_ServicingAssetsAdditionsRecognizedfromSecuritizationTrustsRelatedToTransfersAccountedForAsSales_c3bd2d27-8e8c-4e3e-9e4e-2861b50b4625" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndEquitySecuritiesGainLoss_23318560-d4f5-4747-bd3a-a07b745c5864" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_DebtAndEquitySecuritiesGainLoss_23318560-d4f5-4747-bd3a-a07b745c5864" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GainLossOnInterestRateDerivativeInstruments_8bf6fcc2-c34e-4fb1-a5d6-36be4b33ef22" xlink:href="onit-20240930.xsd#onit_GainLossOnInterestRateDerivativeInstruments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_onit_GainLossOnInterestRateDerivativeInstruments_8bf6fcc2-c34e-4fb1-a5d6-36be4b33ef22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ChangeInFairValueOfMortgageLoansHeldForSale_0c42ae7d-0061-4715-b329-a23c7ec96af4" xlink:href="onit-20240930.xsd#onit_ChangeInFairValueOfMortgageLoansHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_onit_ChangeInFairValueOfMortgageLoansHeldForSale_0c42ae7d-0061-4715-b329-a23c7ec96af4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_a573fe08-d0c1-483c-be62-73db950e53db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_a573fe08-d0c1-483c-be62-73db950e53db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnSalesOfOtherRealEstate_8cee9247-8329-4c73-8d48-7de269b7a52a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnSalesOfOtherRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_GainsLossesOnSalesOfOtherRealEstate_8cee9247-8329-4c73-8d48-7de269b7a52a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSalesOfLoansNet_f52ab66f-4a0a-4950-84f9-c0536329f9d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSalesOfLoansNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_GainLossOnSalesOfLoansNet_f52ab66f-4a0a-4950-84f9-c0536329f9d6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_c883537d-642e-438a-857c-95a3f32719d1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_30a875e5-2310-4bff-a6ea-9e1bd7179a4c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_c883537d-642e-438a-857c-95a3f32719d1" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/AdvancesScheduleofAdvancesPaidonBehalfofBorrowersoronForeclosedPropertiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#AdvancesScheduleofAdvancesPaidonBehalfofBorrowersoronForeclosedPropertiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/AdvancesScheduleofAdvancesPaidonBehalfofBorrowersoronForeclosedPropertiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesOnBehalfOfBorrowersLineItems_5cd8cca9-b18d-46d0-a4fc-36f5057e58dd" xlink:href="onit-20240930.xsd#onit_AdvancesOnBehalfOfBorrowersLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesOnBehalfofBorrowersTable_f8adc8a1-a8f0-4477-a247-cfc5ec675f55" xlink:href="onit-20240930.xsd#onit_AdvancesOnBehalfofBorrowersTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_onit_AdvancesOnBehalfOfBorrowersLineItems_5cd8cca9-b18d-46d0-a4fc-36f5057e58dd" xlink:to="loc_onit_AdvancesOnBehalfofBorrowersTable_f8adc8a1-a8f0-4477-a247-cfc5ec675f55" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6788f04e-a66e-4c4e-bb15-a5f39c68a637" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_onit_AdvancesOnBehalfofBorrowersTable_f8adc8a1-a8f0-4477-a247-cfc5ec675f55" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6788f04e-a66e-4c4e-bb15-a5f39c68a637" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_6788f04e-a66e-4c4e-bb15-a5f39c68a637_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6788f04e-a66e-4c4e-bb15-a5f39c68a637" xlink:to="loc_us-gaap_ReceivableTypeDomain_6788f04e-a66e-4c4e-bb15-a5f39c68a637_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_e9bb4a7f-001a-42c8-9dbd-f0239f060f35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_6788f04e-a66e-4c4e-bb15-a5f39c68a637" xlink:to="loc_us-gaap_ReceivableTypeDomain_e9bb4a7f-001a-42c8-9dbd-f0239f060f35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PrincipalAndInterestMember_164e2e81-acba-4637-ad03-497703c249b2" xlink:href="onit-20240930.xsd#onit_PrincipalAndInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_e9bb4a7f-001a-42c8-9dbd-f0239f060f35" xlink:to="loc_onit_PrincipalAndInterestMember_164e2e81-acba-4637-ad03-497703c249b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TaxesAndInsuranceMember_ce2c6932-f4e3-404f-ac9b-00d03eb8631f" xlink:href="onit-20240930.xsd#onit_TaxesAndInsuranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_e9bb4a7f-001a-42c8-9dbd-f0239f060f35" xlink:to="loc_onit_TaxesAndInsuranceMember_ce2c6932-f4e3-404f-ac9b-00d03eb8631f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForeclosuresAndBankruptcyCostsMember_abb6f7f2-88ca-4a7b-9b93-16fcded8f697" xlink:href="onit-20240930.xsd#onit_ForeclosuresAndBankruptcyCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_e9bb4a7f-001a-42c8-9dbd-f0239f060f35" xlink:to="loc_onit_ForeclosuresAndBankruptcyCostsMember_abb6f7f2-88ca-4a7b-9b93-16fcded8f697" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_7a4bfc52-f719-4ab1-b2b2-d16832fa764f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_onit_AdvancesOnBehalfofBorrowersTable_f8adc8a1-a8f0-4477-a247-cfc5ec675f55" xlink:to="loc_srt_StatementGeographicalAxis_7a4bfc52-f719-4ab1-b2b2-d16832fa764f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_7a4bfc52-f719-4ab1-b2b2-d16832fa764f_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_7a4bfc52-f719-4ab1-b2b2-d16832fa764f" xlink:to="loc_srt_SegmentGeographicalDomain_7a4bfc52-f719-4ab1-b2b2-d16832fa764f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_7a4bfc52-f719-4ab1-b2b2-d16832fa764f" xlink:to="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_NY_fbd9d2a9-52e5-44f6-9b43-e490e3cb1d24" xlink:href="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd#stpr_NY"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:to="loc_stpr_NY_fbd9d2a9-52e5-44f6-9b43-e490e3cb1d24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_FL_a273a533-52d7-4ef6-bfb9-f50141701840" xlink:href="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd#stpr_FL"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:to="loc_stpr_FL_a273a533-52d7-4ef6-bfb9-f50141701840" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_CA_11f0a9a0-67bc-4255-a9be-70dd97d64b01" xlink:href="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd#stpr_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:to="loc_stpr_CA_11f0a9a0-67bc-4255-a9be-70dd97d64b01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_PA_7b80fca8-bed6-470a-bb1a-e0038278008a" xlink:href="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd#stpr_PA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:to="loc_stpr_PA_7b80fca8-bed6-470a-bb1a-e0038278008a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_NJ_ba50e1d5-3b55-4993-862c-b470e7df4873" xlink:href="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd#stpr_NJ"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0307f3b3-7863-445d-ab26-fd852d695cd2" xlink:to="loc_stpr_NJ_ba50e1d5-3b55-4993-862c-b470e7df4873" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InvestorAxis_c6e51925-9023-40a9-bc50-294e3c63feef" xlink:href="onit-20240930.xsd#onit_InvestorAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_onit_AdvancesOnBehalfofBorrowersTable_f8adc8a1-a8f0-4477-a247-cfc5ec675f55" xlink:to="loc_onit_InvestorAxis_c6e51925-9023-40a9-bc50-294e3c63feef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InvestorDomain_c6e51925-9023-40a9-bc50-294e3c63feef_default" xlink:href="onit-20240930.xsd#onit_InvestorDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_onit_InvestorAxis_c6e51925-9023-40a9-bc50-294e3c63feef" xlink:to="loc_onit_InvestorDomain_c6e51925-9023-40a9-bc50-294e3c63feef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InvestorDomain_dab67c77-43cb-4089-a6e6-0003ccf29921" xlink:href="onit-20240930.xsd#onit_InvestorDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_onit_InvestorAxis_c6e51925-9023-40a9-bc50-294e3c63feef" xlink:to="loc_onit_InvestorDomain_dab67c77-43cb-4089-a6e6-0003ccf29921" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GSEMember_afee6c2b-0de1-41f1-b39e-4353a64f4102" xlink:href="onit-20240930.xsd#onit_GSEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_InvestorDomain_dab67c77-43cb-4089-a6e6-0003ccf29921" xlink:to="loc_onit_GSEMember_afee6c2b-0de1-41f1-b39e-4353a64f4102" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GinnieMaeMember_7769b6e3-2007-4693-a629-c4819f8812c8" xlink:href="onit-20240930.xsd#onit_GinnieMaeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_InvestorDomain_dab67c77-43cb-4089-a6e6-0003ccf29921" xlink:to="loc_onit_GinnieMaeMember_7769b6e3-2007-4693-a629-c4819f8812c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NonAgencyMember_220f8a4e-dbb0-4174-9c95-b353b70a7a0a" xlink:href="onit-20240930.xsd#onit_NonAgencyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_InvestorDomain_dab67c77-43cb-4089-a6e6-0003ccf29921" xlink:to="loc_onit_NonAgencyMember_220f8a4e-dbb0-4174-9c95-b353b70a7a0a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesPaymentsOnBehalfOfBorrowerGross_22bf4639-1347-4925-ba83-4521732bc710" xlink:href="onit-20240930.xsd#onit_AdvancesPaymentsOnBehalfOfBorrowerGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_AdvancesOnBehalfOfBorrowersLineItems_5cd8cca9-b18d-46d0-a4fc-36f5057e58dd" xlink:to="loc_onit_AdvancesPaymentsOnBehalfOfBorrowerGross_22bf4639-1347-4925-ba83-4521732bc710" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_e2969a95-cec0-4fe5-a0ff-863a2abf76cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableAllowanceForCreditLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_AdvancesOnBehalfOfBorrowersLineItems_5cd8cca9-b18d-46d0-a4fc-36f5057e58dd" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLosses_e2969a95-cec0-4fe5-a0ff-863a2abf76cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvancesPaymentsOnBehalfOfBorrowerNetOfValuationAllowance_b7f95363-c3c3-480b-ab11-ddcea8bd32aa" xlink:href="onit-20240930.xsd#onit_AdvancesPaymentsOnBehalfOfBorrowerNetOfValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_AdvancesOnBehalfOfBorrowersLineItems_5cd8cca9-b18d-46d0-a4fc-36f5057e58dd" xlink:to="loc_onit_AdvancesPaymentsOnBehalfOfBorrowerNetOfValuationAllowance_b7f95363-c3c3-480b-ab11-ddcea8bd32aa" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/MortgageServicingScheduleofActivityRelatedtoMSRsFairValueMeasurementMethodDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#MortgageServicingScheduleofActivityRelatedtoMSRsFairValueMeasurementMethodDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/MortgageServicingScheduleofActivityRelatedtoMSRsFairValueMeasurementMethodDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueTable_9a14b4b9-b579-474a-b1fe-09def5b9723f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_ServicingAssetsAtFairValueTable_9a14b4b9-b579-474a-b1fe-09def5b9723f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_358f48bc-d8b4-4085-b74e-a6a8bf14a087" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_9a14b4b9-b579-474a-b1fe-09def5b9723f" xlink:to="loc_us-gaap_FinancialInstrumentAxis_358f48bc-d8b4-4085-b74e-a6a8bf14a087" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_358f48bc-d8b4-4085-b74e-a6a8bf14a087_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_358f48bc-d8b4-4085-b74e-a6a8bf14a087" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_358f48bc-d8b4-4085-b74e-a6a8bf14a087_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_358f48bc-d8b4-4085-b74e-a6a8bf14a087" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueAgencyMortgageServicingRightsMember_3d1f2c48-dd82-49dd-ab31-2ee30e92e955" xlink:href="onit-20240930.xsd#onit_FairValueAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_FairValueAgencyMortgageServicingRightsMember_3d1f2c48-dd82-49dd-ab31-2ee30e92e955" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpAndOthersMember_6614ae6b-e89b-4e9d-bff2-67cfffbec416" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpAndOthersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_RithmCapitalCorpAndOthersMember_6614ae6b-e89b-4e9d-bff2-67cfffbec416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TransferredMSRSubjectToPledgedLiabilityMember_9d535a9f-d0db-40ec-a424-0e88062c3695" xlink:href="onit-20240930.xsd#onit_TransferredMSRSubjectToPledgedLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_TransferredMSRSubjectToPledgedLiabilityMember_9d535a9f-d0db-40ec-a424-0e88062c3695" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueGSEMortgageServicingRightsMember_d189481f-4883-4801-869a-09d3b100fd75" xlink:href="onit-20240930.xsd#onit_FairValueGSEMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_FairValueGSEMortgageServicingRightsMember_d189481f-4883-4801-869a-09d3b100fd75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueGNMAMortgageServicingRightsMember_3f49bec8-40d6-41a8-b808-f0b914a8c762" xlink:href="onit-20240930.xsd#onit_FairValueGNMAMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_FairValueGNMAMortgageServicingRightsMember_3f49bec8-40d6-41a8-b808-f0b914a8c762" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_73a9ff43-885a-44cd-a667-81e0b1c46a5b" xlink:href="onit-20240930.xsd#onit_FairValueNonAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_ef0d288c-d3fd-44d2-a384-c781c4318ede" xlink:to="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_73a9ff43-885a-44cd-a667-81e0b1c46a5b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_8c872ddd-49f9-4b1c-970b-ae95ce990c84" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_9a14b4b9-b579-474a-b1fe-09def5b9723f" xlink:to="loc_srt_CounterpartyNameAxis_8c872ddd-49f9-4b1c-970b-ae95ce990c84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_8c872ddd-49f9-4b1c-970b-ae95ce990c84_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_8c872ddd-49f9-4b1c-970b-ae95ce990c84" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_8c872ddd-49f9-4b1c-970b-ae95ce990c84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_997d4b2f-51f9-4649-8ef0-71dea05a303c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_8c872ddd-49f9-4b1c-970b-ae95ce990c84" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_997d4b2f-51f9-4649-8ef0-71dea05a303c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_901246fc-85c1-4efe-938f-912422afbacd" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_997d4b2f-51f9-4649-8ef0-71dea05a303c" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_901246fc-85c1-4efe-938f-912422afbacd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRAssetVehicleLLCMember_0f41b2a6-ddca-43de-911f-f80cf0a802ef" xlink:href="onit-20240930.xsd#onit_MSRAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_997d4b2f-51f9-4649-8ef0-71dea05a303c" xlink:to="loc_onit_MSRAssetVehicleLLCMember_0f41b2a6-ddca-43de-911f-f80cf0a802ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVAssetVehicleLLCMember_314712bc-34f7-40f6-9d76-8d7798894ec2" xlink:href="onit-20240930.xsd#onit_MAVAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_997d4b2f-51f9-4649-8ef0-71dea05a303c" xlink:to="loc_onit_MAVAssetVehicleLLCMember_314712bc-34f7-40f6-9d76-8d7798894ec2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_96edc77a-837c-4119-ab3e-908452576b1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_9a14b4b9-b579-474a-b1fe-09def5b9723f" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_96edc77a-837c-4119-ab3e-908452576b1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_96edc77a-837c-4119-ab3e-908452576b1d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_96edc77a-837c-4119-ab3e-908452576b1d" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_96edc77a-837c-4119-ab3e-908452576b1d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8ccfd5ad-84ac-4fa1-a02e-5d9dc0656805" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_96edc77a-837c-4119-ab3e-908452576b1d" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8ccfd5ad-84ac-4fa1-a02e-5d9dc0656805" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_a1513d60-7c2b-41cc-9b13-2c7eaae118b8" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8ccfd5ad-84ac-4fa1-a02e-5d9dc0656805" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_a1513d60-7c2b-41cc-9b13-2c7eaae118b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_f037b25d-f164-41c7-ba3c-a78b14f423bb" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8ccfd5ad-84ac-4fa1-a02e-5d9dc0656805" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_f037b25d-f164-41c7-ba3c-a78b14f423bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmountRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_d5745386-683c-427b-a773-b6b80aaefe3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_d5745386-683c-427b-a773-b6b80aaefe3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueDisposals_254cf696-1a66-46c7-a450-4013b51097fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueDisposals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueDisposals_254cf696-1a66-46c7-a450-4013b51097fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetsAtFairValueAdditionsRecognizedFromMortgageSales_07cf2c8f-d526-4fac-8dfa-cffb67c2c089" xlink:href="onit-20240930.xsd#onit_ServicingAssetsAtFairValueAdditionsRecognizedFromMortgageSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_onit_ServicingAssetsAtFairValueAdditionsRecognizedFromMortgageSales_07cf2c8f-d526-4fac-8dfa-cffb67c2c089" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAdditions_96c86bbe-f3ca-4a97-85d1-6ab8f3eb81f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAdditions_96c86bbe-f3ca-4a97-85d1-6ab8f3eb81f0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueOtherChangesThatAffectBalance_3693ee20-3fc5-4f40-973f-5265ac8236f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueOtherChangesThatAffectBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueOtherChangesThatAffectBalance_3693ee20-3fc5-4f40-973f-5265ac8236f4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsAbstract_7e6ea0d4-1480-46e7-a43f-6e925da2a53a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsAbstract_7e6ea0d4-1480-46e7-a43f-6e925da2a53a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptions_039434a1-87d7-41ae-afd2-8f79d477f2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsAbstract_7e6ea0d4-1480-46e7-a43f-6e925da2a53a" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptions_039434a1-87d7-41ae-afd2-8f79d477f2d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueOtherChangesInFairValue_e25da33c-f241-493f-b43e-54cbea528b97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueOtherChangesInFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsAbstract_7e6ea0d4-1480-46e7-a43f-6e925da2a53a" xlink:to="loc_us-gaap_ServicingAssetAtFairValueOtherChangesInFairValue_e25da33c-f241-493f-b43e-54cbea528b97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_43de4ee3-a3e8-4040-813e-27f4154b6f2c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetsServiced_17e356b6-5ab7-4d9d-82f2-f83941286680" xlink:href="onit-20240930.xsd#onit_AssetsServiced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_e510c372-fd07-4654-9c73-4dcfd8e0229c" xlink:to="loc_onit_AssetsServiced_17e356b6-5ab7-4d9d-82f2-f83941286680" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_d01d4244-032f-4434-a25f-569dff040494" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_d01d4244-032f-4434-a25f-569dff040494" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_82b71af3-3c81-4343-a061-742ff4cc0b10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_82b71af3-3c81-4343-a061-742ff4cc0b10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetsAtFairValueNetAdditionsSalesRecognized_62468f79-edb5-49b3-b20c-9a4d5178302a" xlink:href="onit-20240930.xsd#onit_ServicingAssetsAtFairValueNetAdditionsSalesRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_onit_ServicingAssetsAtFairValueNetAdditionsSalesRecognized_62468f79-edb5-49b3-b20c-9a4d5178302a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RunoffSettlementsAndOtherFinancingLiability_d77200ee-aa77-4412-ad40-55dd9f4f64e0" xlink:href="onit-20240930.xsd#onit_RunoffSettlementsAndOtherFinancingLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_onit_RunoffSettlementsAndOtherFinancingLiability_d77200ee-aa77-4412-ad40-55dd9f4f64e0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValue_3a1c0a3e-455c-49ee-9c6c-c64abd69d1ae" xlink:href="onit-20240930.xsd#onit_TotalFairValueChangesInServicingLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValue_3a1c0a3e-455c-49ee-9c6c-c64abd69d1ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_a0284833-133b-4547-b2f3-0229b9317a8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_a0284833-133b-4547-b2f3-0229b9317a8a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_5f9b7460-f690-4cf5-9294-a4cc2b920ad5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_5f9b7460-f690-4cf5-9294-a4cc2b920ad5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalMSRReserveFairValueGainsLosses_33c549c9-b269-4cf3-8ec7-33cb4b28c03e" xlink:href="onit-20240930.xsd#onit_TotalMSRReserveFairValueGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_onit_TotalMSRReserveFairValueGainsLosses_33c549c9-b269-4cf3-8ec7-33cb4b28c03e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_84a045c9-3017-434c-a1ec-a8dd7f2e411f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_84a045c9-3017-434c-a1ec-a8dd7f2e411f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetAtFairValueAmountDerecognized_35901b41-1aab-4fd6-b8cb-538936a534be" xlink:href="onit-20240930.xsd#onit_ServicingAssetAtFairValueAmountDerecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_47ed3f44-b7d7-4ee9-b98a-1f7cea765f0e" xlink:to="loc_onit_ServicingAssetAtFairValueAmountDerecognized_35901b41-1aab-4fd6-b8cb-538936a534be" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/MortgageServicingSummaryofDelinquencyStatusofLoansUnderlyingMortgageServicingRightsDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#MortgageServicingSummaryofDelinquencyStatusofLoansUnderlyingMortgageServicingRightsDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/MortgageServicingSummaryofDelinquencyStatusofLoansUnderlyingMortgageServicingRightsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingMortgageLoansLineItems_1caa82a3-b1bd-426c-8267-1488b38fbb10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ParticipatingMortgageLoansLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingMortgageLoansTable_66fbb23b-ca3f-4d49-902b-d60043737f65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ParticipatingMortgageLoansTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_1caa82a3-b1bd-426c-8267-1488b38fbb10" xlink:to="loc_us-gaap_ParticipatingMortgageLoansTable_66fbb23b-ca3f-4d49-902b-d60043737f65" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_f071982a-2ee2-46ef-bf5f-5c94a2be44ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ParticipatingMortgageLoansTable_66fbb23b-ca3f-4d49-902b-d60043737f65" xlink:to="loc_us-gaap_FinancialInstrumentAxis_f071982a-2ee2-46ef-bf5f-5c94a2be44ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f071982a-2ee2-46ef-bf5f-5c94a2be44ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_f071982a-2ee2-46ef-bf5f-5c94a2be44ae" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f071982a-2ee2-46ef-bf5f-5c94a2be44ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_f071982a-2ee2-46ef-bf5f-5c94a2be44ae" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueAgencyMortgageServicingRightsMember_80ea8d6e-cb3f-4a60-ba30-4c744ca596bc" xlink:href="onit-20240930.xsd#onit_FairValueAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:to="loc_onit_FairValueAgencyMortgageServicingRightsMember_80ea8d6e-cb3f-4a60-ba30-4c744ca596bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_491070e6-e741-4e92-a934-7269e0275474" xlink:href="onit-20240930.xsd#onit_FairValueNonAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:to="loc_onit_FairValueNonAgencyMortgageServicingRightsMember_491070e6-e741-4e92-a934-7269e0275474" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueGSEMortgageServicingRightsMember_8c9d5a29-2ab1-4017-8d80-fd39e225a7c0" xlink:href="onit-20240930.xsd#onit_FairValueGSEMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:to="loc_onit_FairValueGSEMortgageServicingRightsMember_8c9d5a29-2ab1-4017-8d80-fd39e225a7c0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueGNMAMortgageServicingRightsMember_a1b6443f-0f1d-4c61-9d7c-1356d273377a" xlink:href="onit-20240930.xsd#onit_FairValueGNMAMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_873f289e-dc8a-46bc-947a-b84234093964" xlink:to="loc_onit_FairValueGNMAMortgageServicingRightsMember_a1b6443f-0f1d-4c61-9d7c-1356d273377a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablesPeriodPastDueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ParticipatingMortgageLoansTable_66fbb23b-ca3f-4d49-902b-d60043737f65" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_0cbaff8c-6552-484d-8eee-ff44db80b0a3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablesPeriodPastDueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueAxis_a9fb2bc3-edd0-4c10-a2e3-5295897d52bc" xlink:to="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_0cbaff8c-6552-484d-8eee-ff44db80b0a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_20ba0b86-47e5-4fa7-890b-2f6a461bb387" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivables30To59DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_0cbaff8c-6552-484d-8eee-ff44db80b0a3" xlink:to="loc_us-gaap_FinancingReceivables30To59DaysPastDueMember_20ba0b86-47e5-4fa7-890b-2f6a461bb387" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_689a747d-0394-4a02-8f4b-5f71a2c5cb89" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivables60To89DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_0cbaff8c-6552-484d-8eee-ff44db80b0a3" xlink:to="loc_us-gaap_FinancingReceivables60To89DaysPastDueMember_689a747d-0394-4a02-8f4b-5f71a2c5cb89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_95f66503-e6f1-47c3-a29c-114949bc82af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablesPeriodPastDueDomain_0cbaff8c-6552-484d-8eee-ff44db80b0a3" xlink:to="loc_us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember_95f66503-e6f1-47c3-a29c-114949bc82af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetsServiced_23236430-6556-4a16-ba8a-561e82ba4264" xlink:href="onit-20240930.xsd#onit_AssetsServiced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_1caa82a3-b1bd-426c-8267-1488b38fbb10" xlink:to="loc_onit_AssetsServiced_23236430-6556-4a16-ba8a-561e82ba4264" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePercentPastDue1_e9fa3cfb-00c5-4c79-940b-3a7452d4acc4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablePercentPastDue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_1caa82a3-b1bd-426c-8267-1488b38fbb10" xlink:to="loc_us-gaap_FinancingReceivablePercentPastDue1_e9fa3cfb-00c5-4c79-940b-3a7452d4acc4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/MortgageServicingScheduleofCompositionofServicingUPBDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#MortgageServicingScheduleofCompositionofServicingUPBDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/MortgageServicingScheduleofCompositionofServicingUPBDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueTable_bd095888-4974-4582-b9e9-b35957f5a204" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:to="loc_us-gaap_ServicingAssetsAtFairValueTable_bd095888-4974-4582-b9e9-b35957f5a204" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_659db17f-4b85-42a9-bf45-4cb6241acd72" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_bd095888-4974-4582-b9e9-b35957f5a204" xlink:to="loc_us-gaap_FinancialInstrumentAxis_659db17f-4b85-42a9-bf45-4cb6241acd72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_659db17f-4b85-42a9-bf45-4cb6241acd72_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_659db17f-4b85-42a9-bf45-4cb6241acd72" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_659db17f-4b85-42a9-bf45-4cb6241acd72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e22a7fcf-1590-4f6e-8fc2-92093dda3e1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_659db17f-4b85-42a9-bf45-4cb6241acd72" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e22a7fcf-1590-4f6e-8fc2-92093dda3e1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OwnedMortgageServicingRightsMember_f936ff52-e695-4b1e-9b72-de6dfea85c80" xlink:href="onit-20240930.xsd#onit_OwnedMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e22a7fcf-1590-4f6e-8fc2-92093dda3e1d" xlink:to="loc_onit_OwnedMortgageServicingRightsMember_f936ff52-e695-4b1e-9b72-de6dfea85c80" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVTransferredMortgageServicingRightsMember_c4ec5dd6-63af-4eee-ae43-756505dc9f1e" xlink:href="onit-20240930.xsd#onit_MAVTransferredMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e22a7fcf-1590-4f6e-8fc2-92093dda3e1d" xlink:to="loc_onit_MAVTransferredMortgageServicingRightsMember_c4ec5dd6-63af-4eee-ae43-756505dc9f1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageServicingRightsTitleRetainedMember_69fd7b1a-7858-41ab-8284-979a98de8a25" xlink:href="onit-20240930.xsd#onit_MortgageServicingRightsTitleRetainedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e22a7fcf-1590-4f6e-8fc2-92093dda3e1d" xlink:to="loc_onit_MortgageServicingRightsTitleRetainedMember_69fd7b1a-7858-41ab-8284-979a98de8a25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_bd095888-4974-4582-b9e9-b35957f5a204" xlink:to="loc_srt_CounterpartyNameAxis_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c7a352f3-daf3-4328-8bf1-7be5c511e327" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_3e5adfa9-11ae-4fa8-bca0-3c5195c56a2d" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c7a352f3-daf3-4328-8bf1-7be5c511e327" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRAssetVehicleLLCMember_c26cd7c8-c333-47fa-946f-dcd2e0ed8f79" xlink:href="onit-20240930.xsd#onit_MSRAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c7a352f3-daf3-4328-8bf1-7be5c511e327" xlink:to="loc_onit_MSRAssetVehicleLLCMember_c26cd7c8-c333-47fa-946f-dcd2e0ed8f79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_ba2e5a20-35d4-47e0-a13d-71394e7e4c28" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_ba2e5a20-35d4-47e0-a13d-71394e7e4c28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetsServiced_9f887a96-9b82-46c7-a7c8-c4f257314e36" xlink:href="onit-20240930.xsd#onit_AssetsServiced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:to="loc_onit_AssetsServiced_9f887a96-9b82-46c7-a7c8-c4f257314e36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_f033f7f4-1da3-4020-bf5f-425e461e7008" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_f033f7f4-1da3-4020-bf5f-425e461e7008" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnpaidPrincipalBalanceOfLoansTransferred_05773d0a-da65-4bd7-9157-ff3856b671f4" xlink:href="onit-20240930.xsd#onit_UnpaidPrincipalBalanceOfLoansTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_fe9dd452-81ad-48be-a7b8-5d3d85c3d27a" xlink:to="loc_onit_UnpaidPrincipalBalanceOfLoansTransferred_05773d0a-da65-4bd7-9157-ff3856b671f4" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/MortgageServicingScheduleofComponentsofServicingandSubservicingFeesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#MortgageServicingScheduleofComponentsofServicingandSubservicingFeesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/MortgageServicingScheduleofComponentsofServicingandSubservicingFeesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ParticipatingMortgageLoansLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingMortgageLoansTable_8cbac178-87dc-43f6-aefc-06e2dce6bc8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ParticipatingMortgageLoansTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_us-gaap_ParticipatingMortgageLoansTable_8cbac178-87dc-43f6-aefc-06e2dce6bc8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_909b4cae-fdf1-4564-a8fc-b42e64eddbf3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ParticipatingMortgageLoansTable_8cbac178-87dc-43f6-aefc-06e2dce6bc8b" xlink:to="loc_srt_CounterpartyNameAxis_909b4cae-fdf1-4564-a8fc-b42e64eddbf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_909b4cae-fdf1-4564-a8fc-b42e64eddbf3_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_909b4cae-fdf1-4564-a8fc-b42e64eddbf3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_909b4cae-fdf1-4564-a8fc-b42e64eddbf3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_59de5089-1e3e-4d5e-b701-cee64ff17e8a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_909b4cae-fdf1-4564-a8fc-b42e64eddbf3" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_59de5089-1e3e-4d5e-b701-cee64ff17e8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVAssetVehicleLLCMember_66137df4-da1c-4add-a666-e08e1783000c" xlink:href="onit-20240930.xsd#onit_MAVAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_59de5089-1e3e-4d5e-b701-cee64ff17e8a" xlink:to="loc_onit_MAVAssetVehicleLLCMember_66137df4-da1c-4add-a666-e08e1783000c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpAndOthersMember_e6a1035d-f58a-4cfb-8e35-51ca613de8eb" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpAndOthersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_59de5089-1e3e-4d5e-b701-cee64ff17e8a" xlink:to="loc_onit_RithmCapitalCorpAndOthersMember_e6a1035d-f58a-4cfb-8e35-51ca613de8eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractuallySpecifiedServicingFeesAmount_561b8ddb-096b-40cc-9017-b63d01aacd14" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractuallySpecifiedServicingFeesAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_us-gaap_ContractuallySpecifiedServicingFeesAmount_561b8ddb-096b-40cc-9017-b63d01aacd14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ContractuallySpecifiedSubservicingFeesAmount_fb5ac757-3000-43d0-bed5-7e4d83e5ab51" xlink:href="onit-20240930.xsd#onit_ContractuallySpecifiedSubservicingFeesAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ContractuallySpecifiedSubservicingFeesAmount_fb5ac757-3000-43d0-bed5-7e4d83e5ab51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ContractuallySpecifiedSubservicingFeesCollectedOnBehalfOfCounterparty_afb136a0-9442-4c0f-bdc5-2ef90daed4dc" xlink:href="onit-20240930.xsd#onit_ContractuallySpecifiedSubservicingFeesCollectedOnBehalfOfCounterparty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ContractuallySpecifiedSubservicingFeesCollectedOnBehalfOfCounterparty_afb136a0-9442-4c0f-bdc5-2ef90daed4dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ContractuallySpecifiedServicingFeesCollectedOnBehalfOfCounterparty_29d793d4-e969-4165-8801-2c80d19a7517" xlink:href="onit-20240930.xsd#onit_ContractuallySpecifiedServicingFeesCollectedOnBehalfOfCounterparty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ContractuallySpecifiedServicingFeesCollectedOnBehalfOfCounterparty_29d793d4-e969-4165-8801-2c80d19a7517" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingFeeCollectedOnBehalfOfCounterparty_5f29579c-0328-4285-8b0d-114fffe9176b" xlink:href="onit-20240930.xsd#onit_ServicingFeeCollectedOnBehalfOfCounterparty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ServicingFeeCollectedOnBehalfOfCounterparty_5f29579c-0328-4285-8b0d-114fffe9176b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ContractuallySpecifiedServicingAndSubservicingFeesAmountTotal_18ec31d9-3dd3-4769-b108-571aba6096ed" xlink:href="onit-20240930.xsd#onit_ContractuallySpecifiedServicingAndSubservicingFeesAmountTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ContractuallySpecifiedServicingAndSubservicingFeesAmountTotal_18ec31d9-3dd3-4769-b108-571aba6096ed" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LateFeeIncomeGeneratedByServicingFinancialAssetsAmount_08cb76a3-bc98-4687-8b5e-811c28d7bfc1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LateFeeIncomeGeneratedByServicingFinancialAssetsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_us-gaap_LateFeeIncomeGeneratedByServicingFinancialAssetsAmount_08cb76a3-bc98-4687-8b5e-811c28d7bfc1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ReverseSubservicingAncillaryIncome_52fdb7cc-2b2b-4710-9b52-e366a16347db" xlink:href="onit-20240930.xsd#onit_ReverseSubservicingAncillaryIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ReverseSubservicingAncillaryIncome_52fdb7cc-2b2b-4710-9b52-e366a16347db" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FloatEarningsEarnedInExchangeForServicingFinancialAssets_bf8d11a1-96e2-4293-ac2f-42b7a8c24ef2" xlink:href="onit-20240930.xsd#onit_FloatEarningsEarnedInExchangeForServicingFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_FloatEarningsEarnedInExchangeForServicingFinancialAssets_bf8d11a1-96e2-4293-ac2f-42b7a8c24ef2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AncillaryFeeIncomeGeneratedByServicingFinancialAssetsAmount_1a3dbfe9-8df6-4e6f-907b-e527b56f94de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AncillaryFeeIncomeGeneratedByServicingFinancialAssetsAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_us-gaap_AncillaryFeeIncomeGeneratedByServicingFinancialAssetsAmount_1a3dbfe9-8df6-4e6f-907b-e527b56f94de" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractuallySpecifiedServicingFeesLateFeesAndAncillaryFeesEarnedInExchangeForServicingFinancialAssets_7b8b03ee-6549-41dc-9b08-f437d47eb361" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractuallySpecifiedServicingFeesLateFeesAndAncillaryFeesEarnedInExchangeForServicingFinancialAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_us-gaap_ContractuallySpecifiedServicingFeesLateFeesAndAncillaryFeesEarnedInExchangeForServicingFinancialAssets_7b8b03ee-6549-41dc-9b08-f437d47eb361" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFees_3ac9dd85-c349-4d12-a71d-62fac77d599a" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ServicingAndSubservicingFees_3ac9dd85-c349-4d12-a71d-62fac77d599a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFeesOwnedMSR_e70c0638-bfd4-48a3-a49a-f3f3d901a3f8" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFeesOwnedMSR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ServicingAndSubservicingFeesOwnedMSR_e70c0638-bfd4-48a3-a49a-f3f3d901a3f8" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFeesTransferredMSR_44ed1aab-ec25-4459-b094-01c576518af8" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFeesTransferredMSR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ServicingAndSubservicingFeesTransferredMSR_44ed1aab-ec25-4459-b094-01c576518af8" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AncillaryFeesTransferredMSR_db1f47aa-28cb-4935-ac1d-1ee1c8b0bcf9" xlink:href="onit-20240930.xsd#onit_AncillaryFeesTransferredMSR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_AncillaryFeesTransferredMSR_db1f47aa-28cb-4935-ac1d-1ee1c8b0bcf9" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold_8b0cbd89-24b2-47ec-8be3-e0db501275c7" xlink:href="onit-20240930.xsd#onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ParticipatingMortgageLoansLineItems_6b463287-e761-491f-9e04-9991423ae92d" xlink:to="loc_onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold_8b0cbd89-24b2-47ec-8be3-e0db501275c7" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofActivityRelatedtoFinancingLiabilityMSRsPledgedDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OtherFinancingLiabilitiesatFairValueScheduleofActivityRelatedtoFinancingLiabilityMSRsPledgedDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofActivityRelatedtoFinancingLiabilityMSRsPledgedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:to="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_452d6d54-7dd8-465e-bc1c-2191b3449e88" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:to="loc_srt_CounterpartyNameAxis_452d6d54-7dd8-465e-bc1c-2191b3449e88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_452d6d54-7dd8-465e-bc1c-2191b3449e88_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_452d6d54-7dd8-465e-bc1c-2191b3449e88" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_452d6d54-7dd8-465e-bc1c-2191b3449e88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_452d6d54-7dd8-465e-bc1c-2191b3449e88" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_b4c499b6-57a9-42f4-9564-59760fcf0b8e" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_b4c499b6-57a9-42f4-9564-59760fcf0b8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRAssetVehicleLLCMember_e6a5aa16-4d73-4665-8522-133e0a56f6ba" xlink:href="onit-20240930.xsd#onit_MSRAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_MSRAssetVehicleLLCMember_e6a5aa16-4d73-4665-8522-133e0a56f6ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpAndOthersMember_b046bedc-e458-4bec-b207-9a60271f538d" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpAndOthersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_RithmCapitalCorpAndOthersMember_b046bedc-e458-4bec-b207-9a60271f538d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpMember_2ed47463-ff7a-4c9c-a179-fd68bab4ce71" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_RithmCapitalCorpMember_2ed47463-ff7a-4c9c-a179-fd68bab4ce71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherMSRCapitalPartnersMember_b9d5660c-0f8b-4630-820c-24efea60ca2c" xlink:href="onit-20240930.xsd#onit_OtherMSRCapitalPartnersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_OtherMSRCapitalPartnersMember_b9d5660c-0f8b-4630-820c-24efea60ca2c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVAssetVehicleLLCMember_e2e8fa11-b653-4397-a6a1-db121ccdd760" xlink:href="onit-20240930.xsd#onit_MAVAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_6b455ed1-5a03-4278-9a80-8dd3ac175ab0" xlink:to="loc_onit_MAVAssetVehicleLLCMember_e2e8fa11-b653-4397-a6a1-db121ccdd760" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_af32e2c4-76bb-47d2-b938-3fd7b59974d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_af32e2c4-76bb-47d2-b938-3fd7b59974d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_af32e2c4-76bb-47d2-b938-3fd7b59974d2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_af32e2c4-76bb-47d2-b938-3fd7b59974d2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_af32e2c4-76bb-47d2-b938-3fd7b59974d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8a8ada81-0dce-4db6-a12e-ee5814063033" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_af32e2c4-76bb-47d2-b938-3fd7b59974d2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8a8ada81-0dce-4db6-a12e-ee5814063033" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_4289a7d3-fd0f-47b7-8455-ea8d71a3ff50" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8a8ada81-0dce-4db6-a12e-ee5814063033" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_4289a7d3-fd0f-47b7-8455-ea8d71a3ff50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0ab5bcf1-a1ab-4bc8-abae-e84556e22878" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0ab5bcf1-a1ab-4bc8-abae-e84556e22878" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_0ab5bcf1-a1ab-4bc8-abae-e84556e22878_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0ab5bcf1-a1ab-4bc8-abae-e84556e22878" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_0ab5bcf1-a1ab-4bc8-abae-e84556e22878_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_02d530f9-17e0-494f-98dd-246044e45561" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0ab5bcf1-a1ab-4bc8-abae-e84556e22878" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_02d530f9-17e0-494f-98dd-246044e45561" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_dc440746-005b-469d-8949-98567b261284" xlink:href="onit-20240930.xsd#onit_OriginalRightstoMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_02d530f9-17e0-494f-98dd-246044e45561" xlink:to="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_dc440746-005b-469d-8949-98567b261284" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_acc615f7-6faa-4228-b513-4ce721cdb30b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueTable_d4d0dc5b-6bb9-46f6-bcaf-213016753c3b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_acc615f7-6faa-4228-b513-4ce721cdb30b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_acc615f7-6faa-4228-b513-4ce721cdb30b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_acc615f7-6faa-4228-b513-4ce721cdb30b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_acc615f7-6faa-4228-b513-4ce721cdb30b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f433eb79-397d-4368-8c1d-c00b9ecb975c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_acc615f7-6faa-4228-b513-4ce721cdb30b" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f433eb79-397d-4368-8c1d-c00b9ecb975c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueAgencyMortgageServicingRightsMember_e881a623-75a5-452e-b954-518fa69939d5" xlink:href="onit-20240930.xsd#onit_FairValueAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f433eb79-397d-4368-8c1d-c00b9ecb975c" xlink:to="loc_onit_FairValueAgencyMortgageServicingRightsMember_e881a623-75a5-452e-b954-518fa69939d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmountRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityAtFairValue_c9372c25-499f-41eb-8b0e-9de186c6b377" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:to="loc_onit_FinancingLiabilityAtFairValue_c9372c25-499f-41eb-8b0e-9de186c6b377" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAssetAtFairValueSales_5a9ef9a0-350f-4396-9ed1-1ee93cc95c3f" xlink:href="onit-20240930.xsd#onit_ServicingAssetAtFairValueSales"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:to="loc_onit_ServicingAssetAtFairValueSales_5a9ef9a0-350f-4396-9ed1-1ee93cc95c3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingLiabilityAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsNetOfAdjustments_04c611a1-711b-4c51-96e5-bb64c1862d1d" xlink:href="onit-20240930.xsd#onit_ServicingLiabilityAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsNetOfAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:to="loc_onit_ServicingLiabilityAtFairValueChangesInFairValueResultingFromChangesInValuationInputsOrChangesInAssumptionsNetOfAdjustments_04c611a1-711b-4c51-96e5-bb64c1862d1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RunoffSettlementsAndOtherFinancingLiability_91726bb6-7246-4e09-9005-3b1957c52272" xlink:href="onit-20240930.xsd#onit_RunoffSettlementsAndOtherFinancingLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:to="loc_onit_RunoffSettlementsAndOtherFinancingLiability_91726bb6-7246-4e09-9005-3b1957c52272" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValueNetOfAdjustments_c8b7b5ac-4b1a-4f42-be11-c4d317e7aadb" xlink:href="onit-20240930.xsd#onit_TotalFairValueChangesInServicingLiabilityAtFairValueNetOfAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtFairValueAmountRollForward_87f1fb30-5041-4bd6-8c05-45da11c54d53" xlink:to="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValueNetOfAdjustments_c8b7b5ac-4b1a-4f42-be11-c4d317e7aadb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityAtFairValue_1cda1017-06c8-4261-b030-cddb486ade97" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityAtFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_772e02a6-9fed-4a04-b3ed-76cf7cf2e622" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_772e02a6-9fed-4a04-b3ed-76cf7cf2e622" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_1b65cac4-55c1-4e92-ba60-8718dff01a81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:to="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_1b65cac4-55c1-4e92-ba60-8718dff01a81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DerecognitionOfFinancingLiability_1a4fef80-472a-4920-ae4d-c604c11860ba" xlink:href="onit-20240930.xsd#onit_DerecognitionOfFinancingLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_3d2cbb4c-6680-4849-9982-e749930f99ad" xlink:to="loc_onit_DerecognitionOfFinancingLiability_1a4fef80-472a-4920-ae4d-c604c11860ba" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofAssetsLiabilitiesRelatedtoMSRTransferAgreementsDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OtherFinancingLiabilitiesatFairValueScheduleofAssetsLiabilitiesRelatedtoMSRTransferAgreementsDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofAssetsLiabilitiesRelatedtoMSRTransferAgreementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingLiabilitiesAtFairValueLineItems_46274269-7ac3-4719-8a96-11931c540040" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingLiabilitiesAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingLiabilitiesAtFairValueTable_a71c917a-ff23-49e1-9cf9-f87fdaf06d12" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingLiabilitiesAtFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingLiabilitiesAtFairValueLineItems_46274269-7ac3-4719-8a96-11931c540040" xlink:to="loc_us-gaap_ServicingLiabilitiesAtFairValueTable_a71c917a-ff23-49e1-9cf9-f87fdaf06d12" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_aaa5bb24-9658-4c3b-9104-17d144748a49" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingLiabilitiesAtFairValueTable_a71c917a-ff23-49e1-9cf9-f87fdaf06d12" xlink:to="loc_srt_CounterpartyNameAxis_aaa5bb24-9658-4c3b-9104-17d144748a49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_aaa5bb24-9658-4c3b-9104-17d144748a49_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_aaa5bb24-9658-4c3b-9104-17d144748a49" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_aaa5bb24-9658-4c3b-9104-17d144748a49_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_dc613ea2-3ced-40db-b52a-92621a290c3d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_aaa5bb24-9658-4c3b-9104-17d144748a49" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_dc613ea2-3ced-40db-b52a-92621a290c3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_a1473c1e-0670-49b9-a014-191002b22e9d" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_dc613ea2-3ced-40db-b52a-92621a290c3d" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_a1473c1e-0670-49b9-a014-191002b22e9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingLiabilitiesAtFairValueTable_a71c917a-ff23-49e1-9cf9-f87fdaf06d12" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_11907839-f60d-45ce-afdf-e400987afcf1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2b95a825-e7dc-4bdc-a36d-83dd6dfb4cc2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_11907839-f60d-45ce-afdf-e400987afcf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_2e9a58d3-5c80-41bb-9059-e3edb7b1b1f1" xlink:href="onit-20240930.xsd#onit_OriginalRightstoMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_11907839-f60d-45ce-afdf-e400987afcf1" xlink:to="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_2e9a58d3-5c80-41bb-9059-e3edb7b1b1f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_90bb9fe2-2da8-42ab-b2f7-00896c92d57f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingLiabilitiesAtFairValueTable_a71c917a-ff23-49e1-9cf9-f87fdaf06d12" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_90bb9fe2-2da8-42ab-b2f7-00896c92d57f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_90bb9fe2-2da8-42ab-b2f7-00896c92d57f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_90bb9fe2-2da8-42ab-b2f7-00896c92d57f" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_90bb9fe2-2da8-42ab-b2f7-00896c92d57f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_cd087aed-1a0e-4240-bb15-7f1639668821" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_90bb9fe2-2da8-42ab-b2f7-00896c92d57f" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_cd087aed-1a0e-4240-bb15-7f1639668821" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_4daaf614-cd6b-4697-a6f1-f31455b4c00e" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_cd087aed-1a0e-4240-bb15-7f1639668821" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_4daaf614-cd6b-4697-a6f1-f31455b4c00e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherFinancingLiabilities_9b77260b-c8cc-4753-afe9-d15464416f3c" xlink:href="onit-20240930.xsd#onit_OtherFinancingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingLiabilitiesAtFairValueLineItems_46274269-7ac3-4719-8a96-11931c540040" xlink:to="loc_onit_OtherFinancingLiabilities_9b77260b-c8cc-4753-afe9-d15464416f3c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofResultsofOperationsinConnectionWithMSRTransferAgreementsthatDoNotQualifyforSaleAccountingDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OtherFinancingLiabilitiesatFairValueScheduleofResultsofOperationsinConnectionWithMSRTransferAgreementsthatDoNotQualifyforSaleAccountingDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueScheduleofResultsofOperationsinConnectionWithMSRTransferAgreementsthatDoNotQualifyforSaleAccountingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_157657cd-7e1c-40c4-ae1c-40580b28beff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_157657cd-7e1c-40c4-ae1c-40580b28beff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_157657cd-7e1c-40c4-ae1c-40580b28beff" xlink:to="loc_srt_CounterpartyNameAxis_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_787e98b4-0571-4193-a17c-482634a74e2e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_271019fd-b4a9-4edd-b5aa-96f5fe6f81cb" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_787e98b4-0571-4193-a17c-482634a74e2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRAssetVehicleLLCMember_fb8eaa94-3631-4446-9203-bea585b4c300" xlink:href="onit-20240930.xsd#onit_MSRAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_787e98b4-0571-4193-a17c-482634a74e2e" xlink:to="loc_onit_MSRAssetVehicleLLCMember_fb8eaa94-3631-4446-9203-bea585b4c300" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpAndOthersMember_aaf80d5f-323f-4463-ac16-dfa2999c3e60" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpAndOthersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_787e98b4-0571-4193-a17c-482634a74e2e" xlink:to="loc_onit_RithmCapitalCorpAndOthersMember_aaf80d5f-323f-4463-ac16-dfa2999c3e60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVAssetVehicleLLCMember_8368d04e-402e-42de-9cea-badb4f3bc436" xlink:href="onit-20240930.xsd#onit_MAVAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_787e98b4-0571-4193-a17c-482634a74e2e" xlink:to="loc_onit_MAVAssetVehicleLLCMember_8368d04e-402e-42de-9cea-badb4f3bc436" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1cc2090a-8baf-4130-95af-9dde0d356cb5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_157657cd-7e1c-40c4-ae1c-40580b28beff" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1cc2090a-8baf-4130-95af-9dde0d356cb5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_1cc2090a-8baf-4130-95af-9dde0d356cb5_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1cc2090a-8baf-4130-95af-9dde0d356cb5" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_1cc2090a-8baf-4130-95af-9dde0d356cb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_9924a37d-19dc-4565-b6e6-aa53b42ec49c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1cc2090a-8baf-4130-95af-9dde0d356cb5" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_9924a37d-19dc-4565-b6e6-aa53b42ec49c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_c5d861db-b6af-4e44-bbb5-afb15b3ab1ec" xlink:href="onit-20240930.xsd#onit_OriginalRightstoMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_9924a37d-19dc-4565-b6e6-aa53b42ec49c" xlink:to="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_c5d861db-b6af-4e44-bbb5-afb15b3ab1ec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_85d233cb-23b8-47fa-9a57-ce433497fece" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_157657cd-7e1c-40c4-ae1c-40580b28beff" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_85d233cb-23b8-47fa-9a57-ce433497fece" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_85d233cb-23b8-47fa-9a57-ce433497fece_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_85d233cb-23b8-47fa-9a57-ce433497fece" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_85d233cb-23b8-47fa-9a57-ce433497fece_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_60535d2f-bc90-471a-8a10-a4c01801720a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_85d233cb-23b8-47fa-9a57-ce433497fece" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_60535d2f-bc90-471a-8a10-a4c01801720a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_d56d67c6-165b-4c17-ba03-4cce7e4efa83" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_60535d2f-bc90-471a-8a10-a4c01801720a" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_d56d67c6-165b-4c17-ba03-4cce7e4efa83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_161876c0-888d-4774-8950-923a38499b29" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_60535d2f-bc90-471a-8a10-a4c01801720a" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_161876c0-888d-4774-8950-923a38499b29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromCollectionOfLoansReceivable_1bda0085-6aa4-4368-b7f2-ffb8cf01835f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromCollectionOfLoansReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_us-gaap_ProceedsFromCollectionOfLoansReceivable_1bda0085-6aa4-4368-b7f2-ffb8cf01835f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_BankServicingFeesRetained_e823fbe2-960d-410d-a6bf-57aa7fe59e56" xlink:href="onit-20240930.xsd#onit_BankServicingFeesRetained"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_onit_BankServicingFeesRetained_e823fbe2-960d-410d-a6bf-57aa7fe59e56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AncillaryAndOtherSettlement_280198cd-c7f1-4161-9fa8-5c5f65ed2ce3" xlink:href="onit-20240930.xsd#onit_AncillaryAndOtherSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_onit_AncillaryAndOtherSettlement_280198cd-c7f1-4161-9fa8-5c5f65ed2ce3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingInterestExpense_1b2b8891-4578-4066-94d9-88a4c67f83f7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingInterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_us-gaap_FinancingInterestExpense_1b2b8891-4578-4066-94d9-88a4c67f83f7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SubservicingFeeRetained_793a96e2-3180-4904-a3a8-a8df925e2731" xlink:href="onit-20240930.xsd#onit_SubservicingFeeRetained"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_onit_SubservicingFeeRetained_793a96e2-3180-4904-a3a8-a8df925e2731" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NetServicingFeeRemittance_0894f034-3fdf-41be-bc15-33308ff77e44" xlink:href="onit-20240930.xsd#onit_NetServicingFeeRemittance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_5884c67d-6053-4ea8-a801-4c85bd922c37" xlink:to="loc_onit_NetServicingFeeRemittance_0894f034-3fdf-41be-bc15-33308ff77e44" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OtherFinancingLiabilitiesatFairValueNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OtherFinancingLiabilitiesatFairValueNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetsAtFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0791b7c1-1eb9-41b5-b636-19156068ffe2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0791b7c1-1eb9-41b5-b636-19156068ffe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_0791b7c1-1eb9-41b5-b636-19156068ffe2_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0791b7c1-1eb9-41b5-b636-19156068ffe2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_0791b7c1-1eb9-41b5-b636-19156068ffe2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_cb59ab86-2e6b-4abc-84f6-2449e33b5aef" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0791b7c1-1eb9-41b5-b636-19156068ffe2" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_cb59ab86-2e6b-4abc-84f6-2449e33b5aef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewRightsToMortgageServicingRightsAgreementsMember_735c5e5d-6588-4119-9840-5c4e090e4048" xlink:href="onit-20240930.xsd#onit_NewRightsToMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_cb59ab86-2e6b-4abc-84f6-2449e33b5aef" xlink:to="loc_onit_NewRightsToMortgageServicingRightsAgreementsMember_735c5e5d-6588-4119-9840-5c4e090e4048" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TwoThousandSeventeenAgreementsandNewRMSRAgreementsMember_88e14c7a-fac9-4d75-a8b0-cd678b7d313c" xlink:href="onit-20240930.xsd#onit_TwoThousandSeventeenAgreementsandNewRMSRAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_cb59ab86-2e6b-4abc-84f6-2449e33b5aef" xlink:to="loc_onit_TwoThousandSeventeenAgreementsandNewRMSRAgreementsMember_88e14c7a-fac9-4d75-a8b0-cd678b7d313c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_148c557c-e479-4205-ad39-97b76da585eb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:to="loc_us-gaap_FinancialInstrumentAxis_148c557c-e479-4205-ad39-97b76da585eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_148c557c-e479-4205-ad39-97b76da585eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_148c557c-e479-4205-ad39-97b76da585eb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_148c557c-e479-4205-ad39-97b76da585eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3528e3e7-ebb5-439e-a1c2-8ffcb3fdcd97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_148c557c-e479-4205-ad39-97b76da585eb" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3528e3e7-ebb5-439e-a1c2-8ffcb3fdcd97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageServicingRightsTitleRetainedMember_e264b62a-07f1-41af-9629-28d551e2a542" xlink:href="onit-20240930.xsd#onit_MortgageServicingRightsTitleRetainedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3528e3e7-ebb5-439e-a1c2-8ffcb3fdcd97" xlink:to="loc_onit_MortgageServicingRightsTitleRetainedMember_e264b62a-07f1-41af-9629-28d551e2a542" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FairValueAgencyMortgageServicingRightsMember_3ddbd851-ad5e-41a9-b197-9b204369b8d2" xlink:href="onit-20240930.xsd#onit_FairValueAgencyMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3528e3e7-ebb5-439e-a1c2-8ffcb3fdcd97" xlink:to="loc_onit_FairValueAgencyMortgageServicingRightsMember_3ddbd851-ad5e-41a9-b197-9b204369b8d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UPBsRelatedToPLSMSRsMember_db45a198-1bdc-4c62-af07-b0b46154de46" xlink:href="onit-20240930.xsd#onit_UPBsRelatedToPLSMSRsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3528e3e7-ebb5-439e-a1c2-8ffcb3fdcd97" xlink:to="loc_onit_UPBsRelatedToPLSMSRsMember_db45a198-1bdc-4c62-af07-b0b46154de46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_1fd48b50-e6ee-4d19-880b-91a42ecc4e39" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:to="loc_dei_LegalEntityAxis_1fd48b50-e6ee-4d19-880b-91a42ecc4e39" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_1fd48b50-e6ee-4d19-880b-91a42ecc4e39_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_1fd48b50-e6ee-4d19-880b-91a42ecc4e39" xlink:to="loc_dei_EntityDomain_1fd48b50-e6ee-4d19-880b-91a42ecc4e39_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5d3932ad-6475-4db2-af25-11e8a249886c" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_1fd48b50-e6ee-4d19-880b-91a42ecc4e39" xlink:to="loc_dei_EntityDomain_5d3932ad-6475-4db2-af25-11e8a249886c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OcwenFinancialCorporationMember_3679c801-7e06-449a-bfc8-fa227b2ceff5" xlink:href="onit-20240930.xsd#onit_OcwenFinancialCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_5d3932ad-6475-4db2-af25-11e8a249886c" xlink:to="loc_onit_OcwenFinancialCorporationMember_3679c801-7e06-449a-bfc8-fa227b2ceff5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_df4caf6f-ca9d-452f-8399-9ed90c85b720" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_5d3932ad-6475-4db2-af25-11e8a249886c" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_df4caf6f-ca9d-452f-8399-9ed90c85b720" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_ca586922-5a9b-4479-af1f-9e6bb9978a64" xlink:to="loc_srt_CounterpartyNameAxis_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_49267560-187b-431a-a065-767fa8e115fb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_09d57d60-e1ff-4d04-a74a-3c5fbac9b70e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_49267560-187b-431a-a065-767fa8e115fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_65089d14-fa79-44e4-8a4e-ac538e980965" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_49267560-187b-431a-a065-767fa8e115fb" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_65089d14-fa79-44e4-8a4e-ac538e980965" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpMember_b0ec232d-eca0-4778-b6ed-8332ab42d4b2" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_49267560-187b-431a-a065-767fa8e115fb" xlink:to="loc_onit_RithmCapitalCorpMember_b0ec232d-eca0-4778-b6ed-8332ab42d4b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_bf9be6bc-fe57-4bf6-81de-1bd3ddf07af0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_bf9be6bc-fe57-4bf6-81de-1bd3ddf07af0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesAmountDerecognized_9598d167-41c4-4e87-b892-d18a0161e998" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransferOfFinancialAssetsAccountedForAsSalesAmountDerecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_us-gaap_TransferOfFinancialAssetsAccountedForAsSalesAmountDerecognized_9598d167-41c4-4e87-b892-d18a0161e998" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAgreementRenewalTerm_1d1477ae-bbdc-4bc3-8cba-626d5bbf741c" xlink:href="onit-20240930.xsd#onit_ServicingAgreementRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_onit_ServicingAgreementRenewalTerm_1d1477ae-bbdc-4bc3-8cba-626d5bbf741c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAgreementsNoticeOfTermination_c48f413d-8cb1-4792-9fd5-9e1a3f5d891b" xlink:href="onit-20240930.xsd#onit_ServicingAgreementsNoticeOfTermination"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_onit_ServicingAgreementsNoticeOfTermination_c48f413d-8cb1-4792-9fd5-9e1a3f5d891b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NumberOfSubservicers_85bada06-8848-420d-b1ac-af0d4aea2a5f" xlink:href="onit-20240930.xsd#onit_NumberOfSubservicers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_onit_NumberOfSubservicers_85bada06-8848-420d-b1ac-af0d4aea2a5f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_170f27a2-64ad-414c-a478-b897e6d9adff" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtFairValueLineItems_9b30f4e9-a9a9-40dc-8f7f-a68be38aeb46" xlink:to="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_170f27a2-64ad-414c-a478-b897e6d9adff" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/MSRValuationAllowanceNetDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#MSRValuationAllowanceNetDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/MSRValuationAllowanceNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_aa36de8e-2d7a-4b46-8a3a-5717dc40aaad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_aa36de8e-2d7a-4b46-8a3a-5717dc40aaad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_aa36de8e-2d7a-4b46-8a3a-5717dc40aaad" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_e922ce3c-6a22-4c75-aa0f-4f6b6e6611e4" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRMember_a24cc1e4-7b0d-426c-b601-b98d782c8419" xlink:href="onit-20240930.xsd#onit_MSRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:to="loc_onit_MSRMember_a24cc1e4-7b0d-426c-b601-b98d782c8419" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_92522283-343b-4d36-af6a-d06f0e1fe095" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_92522283-343b-4d36-af6a-d06f0e1fe095" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_1ef7690b-d274-4e16-b0b6-d9386e7fa6fe" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_1ef7690b-d274-4e16-b0b6-d9386e7fa6fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PledgedMSRLiabilitiesMember_d5492ef7-270b-4380-a110-17270bd4bc2d" xlink:href="onit-20240930.xsd#onit_PledgedMSRLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:to="loc_onit_PledgedMSRLiabilitiesMember_d5492ef7-270b-4380-a110-17270bd4bc2d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ESSFinancingLiabilitiesMember_a4ea3058-896f-40c9-ad59-c95c7cf550f8" xlink:href="onit-20240930.xsd#onit_ESSFinancingLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_4a4d3de2-b9c8-4459-8bfc-b388bf21c431" xlink:to="loc_onit_ESSFinancingLiabilitiesMember_a4ea3058-896f-40c9-ad59-c95c7cf550f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3762359b-673d-4723-b663-af2ced911d48" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherTable_aa36de8e-2d7a-4b46-8a3a-5717dc40aaad" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3762359b-673d-4723-b663-af2ced911d48" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3762359b-673d-4723-b663-af2ced911d48_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3762359b-673d-4723-b663-af2ced911d48" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3762359b-673d-4723-b663-af2ced911d48_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_467299fe-8324-4f19-86f2-3ad1ca16c41b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3762359b-673d-4723-b663-af2ced911d48" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_467299fe-8324-4f19-86f2-3ad1ca16c41b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRMember_9568011f-0c65-44e6-a378-ed8574df34d5" xlink:href="onit-20240930.xsd#onit_MSRMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_467299fe-8324-4f19-86f2-3ad1ca16c41b" xlink:to="loc_onit_MSRMember_9568011f-0c65-44e6-a378-ed8574df34d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_51af25d3-9f17-428f-9e0c-1634a38c19d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_51af25d3-9f17-428f-9e0c-1634a38c19d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityAtFairValue_29c83ee2-ca03-46b6-8e07-4f1dee48ce0a" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_onit_FinancingLiabilityAtFairValue_29c83ee2-ca03-46b6-8e07-4f1dee48ce0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_f40f44bf-608e-4941-8dca-f5f59c019c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_f40f44bf-608e-4941-8dca-f5f59c019c6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValue_b87abff0-f686-4cd8-89dd-fd3951c1ab7b" xlink:href="onit-20240930.xsd#onit_TotalFairValueChangesInServicingLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_onit_TotalFairValueChangesInServicingLiabilityAtFairValue_b87abff0-f686-4cd8-89dd-fd3951c1ab7b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_46e3afcd-7ea6-491d-8291-9822ec4a0ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_46e3afcd-7ea6-491d-8291-9822ec4a0ad7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_e6a0945d-ffa0-47c4-b87d-c32add3168f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_e6a0945d-ffa0-47c4-b87d-c32add3168f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalMSRReserveFairValueGainsLosses_4dc01f2e-83c4-44fb-ba38-98503bcdd240" xlink:href="onit-20240930.xsd#onit_TotalMSRReserveFairValueGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_onit_TotalMSRReserveFairValueGainsLosses_4dc01f2e-83c4-44fb-ba38-98503bcdd240" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherFinancingLiabilities_028c1a43-9ef8-46cd-affb-3be9fcb4db2a" xlink:href="onit-20240930.xsd#onit_OtherFinancingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems_ca7d99d9-b1ef-4489-9342-327bcb128740" xlink:to="loc_onit_OtherFinancingLiabilities_028c1a43-9ef8-46cd-affb-3be9fcb4db2a" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/ReceivablesNarrativeDetail" xlink:type="simple" xlink:href="onit-20240930.xsd#ReceivablesNarrativeDetail"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/ReceivablesNarrativeDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f8062b32-5f40-4af0-be5f-b5b013bdd150" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_d741ee8a-62ea-4464-b1e5-0e70297b6753" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f8062b32-5f40-4af0-be5f-b5b013bdd150" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_d741ee8a-62ea-4464-b1e5-0e70297b6753" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_c0e47550-6eb8-433e-b08c-ba314fed5075" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_d741ee8a-62ea-4464-b1e5-0e70297b6753" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_c0e47550-6eb8-433e-b08c-ba314fed5075" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_c0e47550-6eb8-433e-b08c-ba314fed5075_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c0e47550-6eb8-433e-b08c-ba314fed5075" xlink:to="loc_us-gaap_SegmentDomain_c0e47550-6eb8-433e-b08c-ba314fed5075_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_defc4486-18ef-4307-88c9-72ea52898c3d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_c0e47550-6eb8-433e-b08c-ba314fed5075" xlink:to="loc_us-gaap_SegmentDomain_defc4486-18ef-4307-88c9-72ea52898c3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingMember_2143e612-a7ce-4bfd-8d42-2f2dec690522" xlink:href="onit-20240930.xsd#onit_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_defc4486-18ef-4307-88c9-72ea52898c3d" xlink:to="loc_onit_ServicingMember_2143e612-a7ce-4bfd-8d42-2f2dec690522" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_907fd4e1-03db-4d8f-b4b3-06c9449760e1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_d741ee8a-62ea-4464-b1e5-0e70297b6753" xlink:to="loc_srt_CounterpartyNameAxis_907fd4e1-03db-4d8f-b4b3-06c9449760e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_907fd4e1-03db-4d8f-b4b3-06c9449760e1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_907fd4e1-03db-4d8f-b4b3-06c9449760e1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_907fd4e1-03db-4d8f-b4b3-06c9449760e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_af0cab01-6378-4499-b26f-daf216499f8b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_907fd4e1-03db-4d8f-b4b3-06c9449760e1" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_af0cab01-6378-4499-b26f-daf216499f8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_USVIBureauOfInternalRevenueMember_4417a270-69f5-40dc-aaf7-60e205673dd6" xlink:href="onit-20240930.xsd#onit_USVIBureauOfInternalRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_af0cab01-6378-4499-b26f-daf216499f8b" xlink:to="loc_onit_USVIBureauOfInternalRevenueMember_4417a270-69f5-40dc-aaf7-60e205673dd6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForNotesAndLoansReceivableCurrent_503dea96-15d8-4a9d-abee-4b5284bc33ca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForNotesAndLoansReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f8062b32-5f40-4af0-be5f-b5b013bdd150" xlink:to="loc_us-gaap_AllowanceForNotesAndLoansReceivableCurrent_503dea96-15d8-4a9d-abee-4b5284bc33ca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxReceivable_8eb8eac6-602f-47f6-b4cf-6ae4a3941362" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f8062b32-5f40-4af0-be5f-b5b013bdd150" xlink:to="loc_us-gaap_IncomeTaxReceivable_8eb8eac6-602f-47f6-b4cf-6ae4a3941362" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/ReceivablesScheduleofChangesinallowanceofGovernmentInsuredLoanClaimsDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#ReceivablesScheduleofChangesinallowanceofGovernmentInsuredLoanClaimsDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/ReceivablesScheduleofChangesinallowanceofGovernmentInsuredLoanClaimsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_a17c37c5-9ee7-4afa-b265-5f3f33730fdb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_e64c752d-b626-42d8-bd45-9941b73d4980" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_a17c37c5-9ee7-4afa-b265-5f3f33730fdb" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_e64c752d-b626-42d8-bd45-9941b73d4980" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_40fd5816-2414-4ff3-9db6-b366d52cb8cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablePortfolioSegmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_e64c752d-b626-42d8-bd45-9941b73d4980" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_40fd5816-2414-4ff3-9db6-b366d52cb8cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_40fd5816-2414-4ff3-9db6-b366d52cb8cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_40fd5816-2414-4ff3-9db6-b366d52cb8cc" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_40fd5816-2414-4ff3-9db6-b366d52cb8cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_d32d52d0-1331-4419-86d7-92badedb1296" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivablePortfolioSegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentAxis_40fd5816-2414-4ff3-9db6-b366d52cb8cc" xlink:to="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_d32d52d0-1331-4419-86d7-92badedb1296" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GovernmentInsuredLoansClaimsMember_4b51ad12-f4ce-42f7-8007-d43894405af1" xlink:href="onit-20240930.xsd#onit_GovernmentInsuredLoansClaimsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivablePortfolioSegmentDomain_d32d52d0-1331-4419-86d7-92badedb1296" xlink:to="loc_onit_GovernmentInsuredLoansClaimsMember_4b51ad12-f4ce-42f7-8007-d43894405af1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_953a23f6-f9cf-4612-a292-5f950fdb82b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_a17c37c5-9ee7-4afa-b265-5f3f33730fdb" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_953a23f6-f9cf-4612-a292-5f950fdb82b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForNotesAndLoansReceivableCurrent_cd0bfedf-8abf-4838-bddc-1deeabd457dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForNotesAndLoansReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_953a23f6-f9cf-4612-a292-5f950fdb82b7" xlink:to="loc_us-gaap_AllowanceForNotesAndLoansReceivableCurrent_cd0bfedf-8abf-4838-bddc-1deeabd457dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLossesExpensed_c898b47b-9cdc-4e83-a935-e62e411385f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProvisionForLoanLossesExpensed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_953a23f6-f9cf-4612-a292-5f950fdb82b7" xlink:to="loc_us-gaap_ProvisionForLoanLossesExpensed_c898b47b-9cdc-4e83-a935-e62e411385f0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs_9e451113-0fb8-4343-8fd7-1d61f6a6b201" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward_953a23f6-f9cf-4612-a292-5f950fdb82b7" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableWriteOffs_9e451113-0fb8-4343-8fd7-1d61f6a6b201" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForNotesAndLoansReceivableCurrent_3fa6c448-9a5b-4a51-a1be-fe7d165a6ba1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForNotesAndLoansReceivableCurrent"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/InvestmentinEquityMethodInvesteeandRelatedPartyTransactionsNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#InvestmentinEquityMethodInvesteeandRelatedPartyTransactionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/InvestmentinEquityMethodInvesteeandRelatedPartyTransactionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_srt_CounterpartyNameAxis_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b59c25fc-8e0f-4cd3-9ec2-5ff5a7fdb8ef" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_1730ec4c-d8ef-48b4-a90a-7d9c7d1a981e" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b59c25fc-8e0f-4cd3-9ec2-5ff5a7fdb8ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRAssetVehicleLLCMember_42cfb4e1-205e-43f1-8a09-8da4be700648" xlink:href="onit-20240930.xsd#onit_MSRAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b59c25fc-8e0f-4cd3-9ec2-5ff5a7fdb8ef" xlink:to="loc_onit_MSRAssetVehicleLLCMember_42cfb4e1-205e-43f1-8a09-8da4be700648" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVCanopyHoldCoILLCMember_113c76e3-c739-4bf4-881c-bf711551661d" xlink:href="onit-20240930.xsd#onit_MAVCanopyHoldCoILLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_b59c25fc-8e0f-4cd3-9ec2-5ff5a7fdb8ef" xlink:to="loc_onit_MAVCanopyHoldCoILLCMember_113c76e3-c739-4bf4-881c-bf711551661d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_1252c194-0264-42ff-9a05-ff809a34ec6e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_us-gaap_FinancialInstrumentAxis_1252c194-0264-42ff-9a05-ff809a34ec6e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1252c194-0264-42ff-9a05-ff809a34ec6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1252c194-0264-42ff-9a05-ff809a34ec6e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1252c194-0264-42ff-9a05-ff809a34ec6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b1981f65-194b-4aa0-b823-78a2e2e4a718" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1252c194-0264-42ff-9a05-ff809a34ec6e" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b1981f65-194b-4aa0-b823-78a2e2e4a718" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageServicingRightsTitleTransferredMember_052062c0-90fa-4410-abf0-0a2bf9b6e625" xlink:href="onit-20240930.xsd#onit_MortgageServicingRightsTitleTransferredMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b1981f65-194b-4aa0-b823-78a2e2e4a718" xlink:to="loc_onit_MortgageServicingRightsTitleTransferredMember_052062c0-90fa-4410-abf0-0a2bf9b6e625" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_89e6265c-ee52-4d13-8c30-78174c862884" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_89e6265c-ee52-4d13-8c30-78174c862884" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_89e6265c-ee52-4d13-8c30-78174c862884_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_89e6265c-ee52-4d13-8c30-78174c862884" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_89e6265c-ee52-4d13-8c30-78174c862884_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_e5d8e54a-4f26-40fc-ba26-f16555074765" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_89e6265c-ee52-4d13-8c30-78174c862884" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_e5d8e54a-4f26-40fc-ba26-f16555074765" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVCanopyHoldCoILLCMember_7a452ab5-9dcd-48ba-97eb-a82ba5ce57fe" xlink:href="onit-20240930.xsd#onit_MAVCanopyHoldCoILLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_e5d8e54a-4f26-40fc-ba26-f16555074765" xlink:to="loc_onit_MAVCanopyHoldCoILLCMember_7a452ab5-9dcd-48ba-97eb-a82ba5ce57fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_a427bd91-35cd-497d-8da8-7f5e8583739b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_a427bd91-35cd-497d-8da8-7f5e8583739b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_a427bd91-35cd-497d-8da8-7f5e8583739b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_a427bd91-35cd-497d-8da8-7f5e8583739b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_a427bd91-35cd-497d-8da8-7f5e8583739b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_0b0e8c2c-5c4b-4da7-857d-3d86bed8bbce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_a427bd91-35cd-497d-8da8-7f5e8583739b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_0b0e8c2c-5c4b-4da7-857d-3d86bed8bbce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_7a2cce03-cbfa-4f5f-a62c-783da8fd3b22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_0b0e8c2c-5c4b-4da7-857d-3d86bed8bbce" xlink:to="loc_us-gaap_SubsequentEventMember_7a2cce03-cbfa-4f5f-a62c-783da8fd3b22" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_20435884-3cd0-42c2-ace4-a4e82ef6336f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_us-gaap_DebtInstrumentAxis_20435884-3cd0-42c2-ace4-a4e82ef6336f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_20435884-3cd0-42c2-ace4-a4e82ef6336f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_20435884-3cd0-42c2-ace4-a4e82ef6336f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_20435884-3cd0-42c2-ace4-a4e82ef6336f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_12f70e25-bfd3-423a-b15b-9b9cb368d9f4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_20435884-3cd0-42c2-ace4-a4e82ef6336f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_12f70e25-bfd3-423a-b15b-9b9cb368d9f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OFCSeniorSecuredNotesMember_016f3541-93ba-4c86-b341-354c73ff3fdf" xlink:href="onit-20240930.xsd#onit_OFCSeniorSecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_12f70e25-bfd3-423a-b15b-9b9cb368d9f4" xlink:to="loc_onit_OFCSeniorSecuredNotesMember_016f3541-93ba-4c86-b341-354c73ff3fdf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_2c39c1dc-9ac9-44d5-8252-1116b579d0bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ca56a1a5-f260-4d3f-99d7-6f8c955e4601" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_2c39c1dc-9ac9-44d5-8252-1116b579d0bb" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_2c39c1dc-9ac9-44d5-8252-1116b579d0bb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_2c39c1dc-9ac9-44d5-8252-1116b579d0bb" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_2c39c1dc-9ac9-44d5-8252-1116b579d0bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_08323855-4503-4b01-8e81-78625fe38980" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_2c39c1dc-9ac9-44d5-8252-1116b579d0bb" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_08323855-4503-4b01-8e81-78625fe38980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_188287f7-9f0e-40db-b1f2-942f48e4f055" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_08323855-4503-4b01-8e81-78625fe38980" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodOneMember_188287f7-9f0e-40db-b1f2-942f48e4f055" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_faec6d19-449a-4e18-aa81-2bf452045d3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_08323855-4503-4b01-8e81-78625fe38980" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_faec6d19-449a-4e18-aa81-2bf452045d3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_5287e925-a59c-40d5-a317-5149dcb30737" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_08323855-4503-4b01-8e81-78625fe38980" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodThreeMember_5287e925-a59c-40d5-a317-5149dcb30737" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_d31d9fc8-a0d8-4acf-9c03-8c394e0b89b8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_d31d9fc8-a0d8-4acf-9c03-8c394e0b89b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnpaidPrincipalBalanceOfLoansSubserviced_56b8f85c-9fc3-4710-b6b1-8ee52b29c7fa" xlink:href="onit-20240930.xsd#onit_UnpaidPrincipalBalanceOfLoansSubserviced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_onit_UnpaidPrincipalBalanceOfLoansSubserviced_56b8f85c-9fc3-4710-b6b1-8ee52b29c7fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_60036be9-9c4d-415c-a5b0-9c295f21c67e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_60036be9-9c4d-415c-a5b0-9c295f21c67e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_962666a0-a71b-457f-9e0c-480d6fb20ebe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold_962666a0-a71b-457f-9e0c-480d6fb20ebe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SubservicingAssetNetAssetValue_2fc88412-6072-4a53-b69e-606b8d8ec7f5" xlink:href="onit-20240930.xsd#onit_SubservicingAssetNetAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_onit_SubservicingAssetNetAssetValue_2fc88412-6072-4a53-b69e-606b8d8ec7f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_a4e4caac-22d3-4bca-bc50-cc2542dec289" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_a4e4caac-22d3-4bca-bc50-cc2542dec289" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SaleOfEquityMethodInvestmentPercentageOfAdjustedBookValue_b939f679-4157-4b4e-9b91-31c06d5c0c5e" xlink:href="onit-20240930.xsd#onit_SaleOfEquityMethodInvestmentPercentageOfAdjustedBookValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_onit_SaleOfEquityMethodInvestmentPercentageOfAdjustedBookValue_b939f679-4157-4b4e-9b91-31c06d5c0c5e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_79f91572-1f27-44c7-83e1-43d0f15537f8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_79f91572-1f27-44c7-83e1-43d0f15537f8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtInstrumentAdditionalRedemptionAmount_8a6cbe19-a45b-4315-bda7-8edd07df5515" xlink:href="onit-20240930.xsd#onit_DebtInstrumentAdditionalRedemptionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_onit_DebtInstrumentAdditionalRedemptionAmount_8a6cbe19-a45b-4315-bda7-8edd07df5515" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SaleOfEquityMethodInvestmentReductionInLockoutRestrictionPercentage_25b80a20-a06a-4a9f-b99a-8a45be04e53e" xlink:href="onit-20240930.xsd#onit_SaleOfEquityMethodInvestmentReductionInLockoutRestrictionPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_5f81172c-fc5c-49ba-aa69-e484a957dc68" xlink:to="loc_onit_SaleOfEquityMethodInvestmentReductionInLockoutRestrictionPercentage_25b80a20-a06a-4a9f-b99a-8a45be04e53e" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/OtherFinancingLiabilitiesScheduleofFinancingLiabilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#OtherFinancingLiabilitiesScheduleofFinancingLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/OtherFinancingLiabilitiesScheduleofFinancingLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:to="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d19e6b13-5352-45d7-a4fb-37bb7870f4c3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_srt_RangeAxis_d19e6b13-5352-45d7-a4fb-37bb7870f4c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d19e6b13-5352-45d7-a4fb-37bb7870f4c3_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d19e6b13-5352-45d7-a4fb-37bb7870f4c3" xlink:to="loc_srt_RangeMember_d19e6b13-5352-45d7-a4fb-37bb7870f4c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_95d61d34-233d-4ed5-bd24-85fb899e33d9" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d19e6b13-5352-45d7-a4fb-37bb7870f4c3" xlink:to="loc_srt_RangeMember_95d61d34-233d-4ed5-bd24-85fb899e33d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_673820a1-b866-4227-b1d7-fd912d2faba6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_95d61d34-233d-4ed5-bd24-85fb899e33d9" xlink:to="loc_srt_MinimumMember_673820a1-b866-4227-b1d7-fd912d2faba6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_d3f3fbc8-24a7-48c8-ba3a-f507ef488bcc" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_95d61d34-233d-4ed5-bd24-85fb899e33d9" xlink:to="loc_srt_MaximumMember_d3f3fbc8-24a7-48c8-ba3a-f507ef488bcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b4ad621c-03af-48b7-adcf-8b37a8285391" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6db02798-fcb6-4f94-8d9e-bcdbf5bf2584" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b4ad621c-03af-48b7-adcf-8b37a8285391" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_8e3c978b-3ac3-40b9-ae5d-e9b223c195c0" xlink:href="onit-20240930.xsd#onit_OriginalRightstoMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b4ad621c-03af-48b7-adcf-8b37a8285391" xlink:to="loc_onit_OriginalRightstoMortgageServicingRightsAgreementsMember_8e3c978b-3ac3-40b9-ae5d-e9b223c195c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVMSRSaleAgreementsMember_fe72d219-8d7a-4839-a7b2-958044379382" xlink:href="onit-20240930.xsd#onit_MAVMSRSaleAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b4ad621c-03af-48b7-adcf-8b37a8285391" xlink:to="loc_onit_MAVMSRSaleAgreementsMember_fe72d219-8d7a-4839-a7b2-958044379382" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_840e22be-c9f3-4113-a872-447d930f57a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_us-gaap_DebtInstrumentAxis_840e22be-c9f3-4113-a872-447d930f57a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_840e22be-c9f3-4113-a872-447d930f57a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_840e22be-c9f3-4113-a872-447d930f57a1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_840e22be-c9f3-4113-a872-447d930f57a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e1de01a9-f49d-479f-b117-78f04c5a4e35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_840e22be-c9f3-4113-a872-447d930f57a1" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e1de01a9-f49d-479f-b117-78f04c5a4e35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_bba2d38c-db8c-4272-9eee-3cd4aa32869a" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityMortgageServicingRightsPledgedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e1de01a9-f49d-479f-b117-78f04c5a4e35" xlink:to="loc_onit_FinancingLiabilityMortgageServicingRightsPledgedMember_bba2d38c-db8c-4272-9eee-3cd4aa32869a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ResidentialAssetSecuritizationTrustMember_de6b1ea3-b8ab-49c8-ab55-5cc1521ee232" xlink:href="onit-20240930.xsd#onit_ResidentialAssetSecuritizationTrustMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e1de01a9-f49d-479f-b117-78f04c5a4e35" xlink:to="loc_onit_ResidentialAssetSecuritizationTrustMember_de6b1ea3-b8ab-49c8-ab55-5cc1521ee232" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_fcba7546-ae3d-46d3-91b1-0f59ccaef315" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_fcba7546-ae3d-46d3-91b1-0f59ccaef315" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_fcba7546-ae3d-46d3-91b1-0f59ccaef315_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_fcba7546-ae3d-46d3-91b1-0f59ccaef315" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_fcba7546-ae3d-46d3-91b1-0f59ccaef315_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_7503698c-b978-4ea9-9773-a87fd5316cd7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_fcba7546-ae3d-46d3-91b1-0f59ccaef315" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_7503698c-b978-4ea9-9773-a87fd5316cd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilityExcessServicingSpreadMember_bbb25f79-1273-4559-a6b1-41fc513b0c19" xlink:href="onit-20240930.xsd#onit_FinancingLiabilityExcessServicingSpreadMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_7503698c-b978-4ea9-9773-a87fd5316cd7" xlink:to="loc_onit_FinancingLiabilityExcessServicingSpreadMember_bbb25f79-1273-4559-a6b1-41fc513b0c19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_41d4d760-a3a4-4103-a27e-0f4b0bafa288" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_srt_CounterpartyNameAxis_41d4d760-a3a4-4103-a27e-0f4b0bafa288" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_41d4d760-a3a4-4103-a27e-0f4b0bafa288_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_41d4d760-a3a4-4103-a27e-0f4b0bafa288" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_41d4d760-a3a4-4103-a27e-0f4b0bafa288_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_f08119fa-6089-4887-9a90-87b4b4624cce" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_41d4d760-a3a4-4103-a27e-0f4b0bafa288" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_f08119fa-6089-4887-9a90-87b4b4624cce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherCounterpartiesForPledgedMSRLiabMember_8827d0af-01a4-4c13-b52a-f05c7f92a975" xlink:href="onit-20240930.xsd#onit_OtherCounterpartiesForPledgedMSRLiabMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_f08119fa-6089-4887-9a90-87b4b4624cce" xlink:to="loc_onit_OtherCounterpartiesForPledgedMSRLiabMember_8827d0af-01a4-4c13-b52a-f05c7f92a975" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_34ac5cd2-a2a4-4a01-8979-cde425b382d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4c4122c8-9f65-49e1-b128-0758e71b9599" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_34ac5cd2-a2a4-4a01-8979-cde425b382d6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_34ac5cd2-a2a4-4a01-8979-cde425b382d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_34ac5cd2-a2a4-4a01-8979-cde425b382d6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_34ac5cd2-a2a4-4a01-8979-cde425b382d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_338c6f84-494c-428d-9cb6-5a824fa53f53" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_34ac5cd2-a2a4-4a01-8979-cde425b382d6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_338c6f84-494c-428d-9cb6-5a824fa53f53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingLiabilitiesMember_4434f6ea-dcc4-4727-8de3-765a6ebcd7af" xlink:href="onit-20240930.xsd#onit_FinancingLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_338c6f84-494c-428d-9cb6-5a824fa53f53" xlink:to="loc_onit_FinancingLiabilitiesMember_4434f6ea-dcc4-4727-8de3-765a6ebcd7af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherFinancingLiabilities_4688d3df-3e40-4345-93bf-16a63c0143e6" xlink:href="onit-20240930.xsd#onit_OtherFinancingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:to="loc_onit_OtherFinancingLiabilities_4688d3df-3e40-4345-93bf-16a63c0143e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_471d5fb8-dfa6-4286-bb3c-2c72dba8e909" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_471d5fb8-dfa6-4286-bb3c-2c72dba8e909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFees_5b1555b6-764b-47f9-be77-5cb2e744247c" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:to="loc_onit_ServicingAndSubservicingFees_5b1555b6-764b-47f9-be77-5cb2e744247c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ProceedsFromExcessServicingSpreadFinancing_a91850b6-aadd-498d-8e9e-d5841fcb2f93" xlink:href="onit-20240930.xsd#onit_ProceedsFromExcessServicingSpreadFinancing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_49c07bbd-0f6f-47f9-b90d-d3453e57294b" xlink:to="loc_onit_ProceedsFromExcessServicingSpreadFinancing_a91850b6-aadd-498d-8e9e-d5841fcb2f93" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsScheduleofMatchFundedLiabilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsScheduleofMatchFundedLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsScheduleofMatchFundedLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_6237701c-bca0-48cb-aa15-5401facc8b3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_DebtInstrumentTable_6237701c-bca0-48cb-aa15-5401facc8b3c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_6237701c-bca0-48cb-aa15-5401facc8b3c" xlink:to="loc_us-gaap_DebtInstrumentAxis_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_ef8df7c6-f85c-46b2-b77c-d1f6d856b76c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SeriesTwoThousandFifteenVariableFundingNotesMember_e32a1f2c-1df7-4936-ad0b-85395c4a47f9" xlink:href="onit-20240930.xsd#onit_SeriesTwoThousandFifteenVariableFundingNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:to="loc_onit_SeriesTwoThousandFifteenVariableFundingNotesMember_e32a1f2c-1df7-4936-ad0b-85395c4a47f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SeriesTwoThousandFifteenVariableFundingNotesOneMember_3b0dd740-4615-4179-933f-b97fac2c2377" xlink:href="onit-20240930.xsd#onit_SeriesTwoThousandFifteenVariableFundingNotesOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:to="loc_onit_SeriesTwoThousandFifteenVariableFundingNotesOneMember_3b0dd740-4615-4179-933f-b97fac2c2377" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_EBOAdvanceFacilityMember_b58ba4e7-8c7b-47d9-9516-81f5cac17c7f" xlink:href="onit-20240930.xsd#onit_EBOAdvanceFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:to="loc_onit_EBOAdvanceFacilityMember_b58ba4e7-8c7b-47d9-9516-81f5cac17c7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MatchFundedLiabiltiesMember_692fc48a-e5c7-4c8d-a811-3d73e392f153" xlink:href="onit-20240930.xsd#onit_MatchFundedLiabiltiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_aeb30593-653b-4fde-ad67-5efdd6babb8b" xlink:to="loc_onit_MatchFundedLiabiltiesMember_692fc48a-e5c7-4c8d-a811-3d73e392f153" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_6237701c-bca0-48cb-aa15-5401facc8b3c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_54897a04-67a4-4e9c-81ea-eabf3ac50790" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_d0a680fc-8fc1-4aaf-849a-d11b2438e0c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_54897a04-67a4-4e9c-81ea-eabf3ac50790" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OcwenMasterAdvanceReceivablesTrustMember_8a517355-b5a4-45df-98ba-d4f9fe3d3019" xlink:href="onit-20240930.xsd#onit_OcwenMasterAdvanceReceivablesTrustMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_54897a04-67a4-4e9c-81ea-eabf3ac50790" xlink:to="loc_onit_OcwenMasterAdvanceReceivablesTrustMember_8a517355-b5a4-45df-98ba-d4f9fe3d3019" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OcwenFreddieAdvanceFundingMember_cb937901-87ae-4849-8193-814cdb54316b" xlink:href="onit-20240930.xsd#onit_OcwenFreddieAdvanceFundingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_54897a04-67a4-4e9c-81ea-eabf3ac50790" xlink:to="loc_onit_OcwenFreddieAdvanceFundingMember_cb937901-87ae-4849-8193-814cdb54316b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_5d5baa58-b79f-40ad-9ed1-ccc5b9f472a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_5d5baa58-b79f-40ad-9ed1-ccc5b9f472a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_0f820151-ae70-49ec-9dc3-26e7b3ab3bed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_0f820151-ae70-49ec-9dc3-26e7b3ab3bed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_2c474def-5910-459f-be64-7b9b745254e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount_2c474def-5910-459f-be64-7b9b745254e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_86e0b0ac-eb7d-4813-9c48-345bf88a0f35" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_86e0b0ac-eb7d-4813-9c48-345bf88a0f35" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_1ef40379-821d-4ccf-aa58-ccc18298c7ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_1ef40379-821d-4ccf-aa58-ccc18298c7ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_e8383f94-a80d-427b-bd30-e89632a69dfe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_87d2da43-7110-4ede-b61f-a3d7ef843f18" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_e8383f94-a80d-427b-bd30-e89632a69dfe" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsScheduleofMortgageLoanWarehouseandMSRFinancingFacilitiesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsScheduleofMortgageLoanWarehouseandMSRFinancingFacilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsScheduleofMortgageLoanWarehouseandMSRFinancingFacilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_7cc5ce55-7e29-4a96-95fc-8e991dd374be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_us-gaap_CreditFacilityAxis_7cc5ce55-7e29-4a96-95fc-8e991dd374be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_7cc5ce55-7e29-4a96-95fc-8e991dd374be_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_7cc5ce55-7e29-4a96-95fc-8e991dd374be" xlink:to="loc_us-gaap_CreditFacilityDomain_7cc5ce55-7e29-4a96-95fc-8e991dd374be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_7cc5ce55-7e29-4a96-95fc-8e991dd374be" xlink:to="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_October2024MasterRepurchaseAgreementMember_d2f80e27-59f9-4652-a740-280fc426f245" xlink:href="onit-20240930.xsd#onit_October2024MasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_October2024MasterRepurchaseAgreementMember_d2f80e27-59f9-4652-a740-280fc426f245" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NoMaturityMortgageWarehouseAgreementMember_85f134f8-82cc-4a74-9ca7-5fa163fe083a" xlink:href="onit-20240930.xsd#onit_NoMaturityMortgageWarehouseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_NoMaturityMortgageWarehouseAgreementMember_85f134f8-82cc-4a74-9ca7-5fa163fe083a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ParticipationAgreementMember_b7af4e9e-9af4-404c-ba20-af68ed36d001" xlink:href="onit-20240930.xsd#onit_ParticipationAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_ParticipationAgreementMember_b7af4e9e-9af4-404c-ba20-af68ed36d001" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_September2024MasterRepurchaseAgreementMember_c2580fd9-eea3-4bc4-b18b-1ef7b7b94ffb" xlink:href="onit-20240930.xsd#onit_September2024MasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_September2024MasterRepurchaseAgreementMember_c2580fd9-eea3-4bc4-b18b-1ef7b7b94ffb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_June2024MasterRepurchaseAgreement2Member_0d60f100-e042-4947-bc18-75ce27fca3b4" xlink:href="onit-20240930.xsd#onit_June2024MasterRepurchaseAgreement2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_June2024MasterRepurchaseAgreement2Member_0d60f100-e042-4947-bc18-75ce27fca3b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_January2024MortgageWarehouseAgreementMember_8fe6f1ec-df71-4010-b526-c4ed2e8c3e33" xlink:href="onit-20240930.xsd#onit_January2024MortgageWarehouseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_January2024MortgageWarehouseAgreementMember_8fe6f1ec-df71-4010-b526-c4ed2e8c3e33" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_March2024MortgageWarehouseAgreement2Member_243f9792-08c4-4999-af5a-8268e468fb7f" xlink:href="onit-20240930.xsd#onit_March2024MortgageWarehouseAgreement2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_March2024MortgageWarehouseAgreement2Member_243f9792-08c4-4999-af5a-8268e468fb7f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MortgageWarehouseAgreementMember_643f39ec-b3eb-4cb1-afe2-b8ee3a00d2c7" xlink:href="onit-20240930.xsd#onit_MortgageWarehouseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_MortgageWarehouseAgreementMember_643f39ec-b3eb-4cb1-afe2-b8ee3a00d2c7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MasterRepurchaseAgreement2Member_32feaa04-7b58-4426-8929-9ebd4c7476df" xlink:href="onit-20240930.xsd#onit_MasterRepurchaseAgreement2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_MasterRepurchaseAgreement2Member_32feaa04-7b58-4426-8929-9ebd4c7476df" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanAndSecurityAgreementMember_047677a1-e54d-4a7a-a568-c925ed152aa2" xlink:href="onit-20240930.xsd#onit_LoanAndSecurityAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_LoanAndSecurityAgreementMember_047677a1-e54d-4a7a-a568-c925ed152aa2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_April2024MasterRepurchaseAgreementMember_eb8bab9e-76df-4a6d-b486-65c762f0dd7a" xlink:href="onit-20240930.xsd#onit_April2024MasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_April2024MasterRepurchaseAgreementMember_eb8bab9e-76df-4a6d-b486-65c762f0dd7a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_A200MillionApril2024MasterRepurchaseAgreementMember_ab1ea608-6ddd-4d00-9904-9e3f9eac7227" xlink:href="onit-20240930.xsd#onit_A200MillionApril2024MasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_A200MillionApril2024MasterRepurchaseAgreementMember_ab1ea608-6ddd-4d00-9904-9e3f9eac7227" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLIT2023NotesMember_61129cb3-a493-4463-a8cd-dbfd4982a59b" xlink:href="onit-20240930.xsd#onit_OLIT2023NotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OLIT2023NotesMember_61129cb3-a493-4463-a8cd-dbfd4982a59b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITNotesFY2022Member_0bf32bd6-190e-4c5d-9db5-5bae49a155cb" xlink:href="onit-20240930.xsd#onit_OLITNotesFY2022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OLITNotesFY2022Member_0bf32bd6-190e-4c5d-9db5-5bae49a155cb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITAssetBackedNotesSeries2024HBIMember_beb0825c-aae5-4be6-b98f-d7dea1a29709" xlink:href="onit-20240930.xsd#onit_OLITAssetBackedNotesSeries2024HBIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OLITAssetBackedNotesSeries2024HBIMember_beb0825c-aae5-4be6-b98f-d7dea1a29709" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AgencyMortgageServicingRightsFinancingFacilityMember_a028d88b-f0c4-45b7-a8b8-d05bf0d9c416" xlink:href="onit-20240930.xsd#onit_AgencyMortgageServicingRightsFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_AgencyMortgageServicingRightsFinancingFacilityMember_a028d88b-f0c4-45b7-a8b8-d05bf0d9c416" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_GinnieMaeMortgageServicingRightsFinancingFacilityMember_c9f18a93-8ea2-4779-8c5d-7c060f2d4d28" xlink:href="onit-20240930.xsd#onit_GinnieMaeMortgageServicingRightsFinancingFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_GinnieMaeMortgageServicingRightsFinancingFacilityMember_c9f18a93-8ea2-4779-8c5d-7c060f2d4d28" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OcwenExcessSpreadCollateralizedNotesSeries2019PLS1ClassAMember_61cb76b7-09c7-459d-9ef0-0a6585ceb0c0" xlink:href="onit-20240930.xsd#onit_OcwenExcessSpreadCollateralizedNotesSeries2019PLS1ClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OcwenExcessSpreadCollateralizedNotesSeries2019PLS1ClassAMember_61cb76b7-09c7-459d-9ef0-0a6585ceb0c0" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PLS1NotesIssuerMembershipInterestMasterRepurchaseAgreementMember_034a1fe2-7bc7-41a9-9068-97a042859022" xlink:href="onit-20240930.xsd#onit_PLS1NotesIssuerMembershipInterestMasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_PLS1NotesIssuerMembershipInterestMasterRepurchaseAgreementMember_034a1fe2-7bc7-41a9-9068-97a042859022" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OASISSeries20141Member_ec8f317b-3ae3-46d1-a49e-2db4a004ba07" xlink:href="onit-20240930.xsd#onit_OASISSeries20141Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OASISSeries20141Member_ec8f317b-3ae3-46d1-a49e-2db4a004ba07" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AgencyMSRFinancingFacilityRevolvingLoanMember_13b3a054-99a1-4292-9533-d568c38f687f" xlink:href="onit-20240930.xsd#onit_AgencyMSRFinancingFacilityRevolvingLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_AgencyMSRFinancingFacilityRevolvingLoanMember_13b3a054-99a1-4292-9533-d568c38f687f" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_September2024LoanAndSecurityAgreementMember_96bba375-1631-4f4a-b7dc-4845851057fe" xlink:href="onit-20240930.xsd#onit_September2024LoanAndSecurityAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_September2024LoanAndSecurityAgreementMember_96bba375-1631-4f4a-b7dc-4845851057fe" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SecuritiesMasterRepurchaseAgreementMember_12a4c361-af12-40cd-b59c-dd1d0a8a4341" xlink:href="onit-20240930.xsd#onit_SecuritiesMasterRepurchaseAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_SecuritiesMasterRepurchaseAgreementMember_12a4c361-af12-40cd-b59c-dd1d0a8a4341" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITAssetBackedNotesSeries2024HB2Member_56e86d82-fc2b-4fd5-a8db-b264053a2485" xlink:href="onit-20240930.xsd#onit_OLITAssetBackedNotesSeries2024HB2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_1936c9ab-568d-4665-96eb-ab81671cef4d" xlink:to="loc_onit_OLITAssetBackedNotesSeries2024HB2Member_56e86d82-fc2b-4fd5-a8db-b264053a2485" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_c784d68d-5771-450a-bbef-5a8d0131c90a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_us-gaap_DebtInstrumentAxis_c784d68d-5771-450a-bbef-5a8d0131c90a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_c784d68d-5771-450a-bbef-5a8d0131c90a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_c784d68d-5771-450a-bbef-5a8d0131c90a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_c784d68d-5771-450a-bbef-5a8d0131c90a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a4f610e5-d58d-431d-af49-e07d0af6dce9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_c784d68d-5771-450a-bbef-5a8d0131c90a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a4f610e5-d58d-431d-af49-e07d0af6dce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_8fcc6d35-dec4-444c-b55d-3b38d69fb4cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a4f610e5-d58d-431d-af49-e07d0af6dce9" xlink:to="loc_us-gaap_SecuredDebtMember_8fcc6d35-dec4-444c-b55d-3b38d69fb4cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRFinancingFacilitiesMember_e824b859-242c-4aae-8f11-67c381156ed2" xlink:href="onit-20240930.xsd#onit_MSRFinancingFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a4f610e5-d58d-431d-af49-e07d0af6dce9" xlink:to="loc_onit_MSRFinancingFacilitiesMember_e824b859-242c-4aae-8f11-67c381156ed2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OASISSeries20141Member_cf817eba-cba0-4d2b-8e2f-8208aa5f1335" xlink:href="onit-20240930.xsd#onit_OASISSeries20141Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_a4f610e5-d58d-431d-af49-e07d0af6dce9" xlink:to="loc_onit_OASISSeries20141Member_cf817eba-cba0-4d2b-8e2f-8208aa5f1335" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_ad321031-d185-4d7f-861e-cf2c581b83ab" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_ad321031-d185-4d7f-861e-cf2c581b83ab" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_ad321031-d185-4d7f-861e-cf2c581b83ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_ad321031-d185-4d7f-861e-cf2c581b83ab" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_ad321031-d185-4d7f-861e-cf2c581b83ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_f535912d-d151-40d4-9c9c-ec3d13e45f80" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_ad321031-d185-4d7f-861e-cf2c581b83ab" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_f535912d-d151-40d4-9c9c-ec3d13e45f80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarehouseAgreementBorrowingsMember_13f71f1c-935a-4355-8bef-32ce8097b153" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WarehouseAgreementBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_f535912d-d151-40d4-9c9c-ec3d13e45f80" xlink:to="loc_us-gaap_WarehouseAgreementBorrowingsMember_13f71f1c-935a-4355-8bef-32ce8097b153" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITNoteDiscountAndAmortizationAxis_f17a6503-2694-407d-8d56-857eb861a2a2" xlink:href="onit-20240930.xsd#onit_OLITNoteDiscountAndAmortizationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_onit_OLITNoteDiscountAndAmortizationAxis_f17a6503-2694-407d-8d56-857eb861a2a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITNoteDiscountAndAmortizationDomain_f17a6503-2694-407d-8d56-857eb861a2a2_default" xlink:href="onit-20240930.xsd#onit_OLITNoteDiscountAndAmortizationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_onit_OLITNoteDiscountAndAmortizationAxis_f17a6503-2694-407d-8d56-857eb861a2a2" xlink:to="loc_onit_OLITNoteDiscountAndAmortizationDomain_f17a6503-2694-407d-8d56-857eb861a2a2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OLITNoteDiscountAndAmortizationDomain_ec9df125-a9fb-43fa-b532-9bbbf38cacb9" xlink:href="onit-20240930.xsd#onit_OLITNoteDiscountAndAmortizationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_onit_OLITNoteDiscountAndAmortizationAxis_f17a6503-2694-407d-8d56-857eb861a2a2" xlink:to="loc_onit_OLITNoteDiscountAndAmortizationDomain_ec9df125-a9fb-43fa-b532-9bbbf38cacb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_c9687a62-d0a8-48d7-8920-206143f9e542" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OLITNoteDiscountAndAmortizationDomain_ec9df125-a9fb-43fa-b532-9bbbf38cacb9" xlink:to="loc_us-gaap_SecuredDebtMember_c9687a62-d0a8-48d7-8920-206143f9e542" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_3cd78b31-5f35-447a-ba3c-91576cc93a34" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_3cd78b31-5f35-447a-ba3c-91576cc93a34" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3cd78b31-5f35-447a-ba3c-91576cc93a34_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3cd78b31-5f35-447a-ba3c-91576cc93a34" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3cd78b31-5f35-447a-ba3c-91576cc93a34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_7667e0de-eeec-4ddd-aedc-7e7387265ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3cd78b31-5f35-447a-ba3c-91576cc93a34" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_7667e0de-eeec-4ddd-aedc-7e7387265ef1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_f6f50762-e631-44ff-9b7d-b2997bf6f9a6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_7667e0de-eeec-4ddd-aedc-7e7387265ef1" xlink:to="loc_us-gaap_SubsequentEventMember_f6f50762-e631-44ff-9b7d-b2997bf6f9a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_d4deb0c6-972a-40b3-80de-7c9e7b687527" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_srt_OwnershipAxis_d4deb0c6-972a-40b3-80de-7c9e7b687527" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_d4deb0c6-972a-40b3-80de-7c9e7b687527_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_d4deb0c6-972a-40b3-80de-7c9e7b687527" xlink:to="loc_srt_OwnershipDomain_d4deb0c6-972a-40b3-80de-7c9e7b687527_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_ead91093-2154-4441-9583-596012305e6d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_d4deb0c6-972a-40b3-80de-7c9e7b687527" xlink:to="loc_srt_OwnershipDomain_ead91093-2154-4441-9583-596012305e6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PLSIssuerMember_cd9174d5-1337-4a47-b3a2-0af709f8df1f" xlink:href="onit-20240930.xsd#onit_PLSIssuerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_ead91093-2154-4441-9583-596012305e6d" xlink:to="loc_onit_PLSIssuerMember_cd9174d5-1337-4a47-b3a2-0af709f8df1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_a2688822-57ed-49ee-ba45-c0e07d518832" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3eca43e1-973a-4afd-bd80-5fa8109beb1c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_a2688822-57ed-49ee-ba45-c0e07d518832" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a2688822-57ed-49ee-ba45-c0e07d518832_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a2688822-57ed-49ee-ba45-c0e07d518832" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a2688822-57ed-49ee-ba45-c0e07d518832_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a5950c16-2083-435d-b2b4-55b3db986e96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_a2688822-57ed-49ee-ba45-c0e07d518832" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a5950c16-2083-435d-b2b4-55b3db986e96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FinancingAgreementsMember_75549455-1489-4afd-a996-6b7937547caa" xlink:href="onit-20240930.xsd#onit_FinancingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a5950c16-2083-435d-b2b4-55b3db986e96" xlink:to="loc_onit_FinancingAgreementsMember_75549455-1489-4afd-a996-6b7937547caa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SecuritizationNotesMember_c5898f8f-618a-47b7-afa6-a4cfd1d624c5" xlink:href="onit-20240930.xsd#onit_SecuritizationNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a5950c16-2083-435d-b2b4-55b3db986e96" xlink:to="loc_onit_SecuritizationNotesMember_c5898f8f-618a-47b7-afa6-a4cfd1d624c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_83d12562-9fec-40da-b5b9-729295cc4704" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_83d12562-9fec-40da-b5b9-729295cc4704" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_2b802b42-36d2-40d4-b505-4103898e8164" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_2b802b42-36d2-40d4-b505-4103898e8164" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_46ea1438-a649-4a5d-a0ba-982f6c5188f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_46ea1438-a649-4a5d-a0ba-982f6c5188f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_efa307d1-a9f8-4f4b-b867-17c94642138c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_efa307d1-a9f8-4f4b-b867-17c94642138c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_044f3d1c-6ccc-4872-bd4c-fee0577115a5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LongTermDebt_044f3d1c-6ccc-4872-bd4c-fee0577115a5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_8b4151d0-97a1-43ec-b4a4-0d7cfa675f74" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_8b4151d0-97a1-43ec-b4a4-0d7cfa675f74" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2078b470-0b53-47ad-98da-46324de10d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2078b470-0b53-47ad-98da-46324de10d0a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtTerm_689eed1c-0ea9-46cb-8bf2-084dcab926d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LongTermDebtTerm_689eed1c-0ea9-46cb-8bf2-084dcab926d8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_ff61c4b3-2b7b-4259-8cdc-4b26e5798e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_ff61c4b3-2b7b-4259-8cdc-4b26e5798e4d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_0fbaf994-35b1-412c-9add-adabe41ebf3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_0fbaf994-35b1-412c-9add-adabe41ebf3c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_12924ef9-cb8c-4f4b-a5c1-08641f5ff489" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_12924ef9-cb8c-4f4b-a5c1-08641f5ff489" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LongTermDebtCertificatePeriodIncrease_adde1a02-c447-4dff-a00c-24162f0a122f" xlink:href="onit-20240930.xsd#onit_LongTermDebtCertificatePeriodIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_onit_LongTermDebtCertificatePeriodIncrease_adde1a02-c447-4dff-a00c-24162f0a122f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_ffb7b09f-f0ee-48f1-8c2b-c60b97781816" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_7859bc4e-14ab-4955-82ae-10515051d742" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_ffb7b09f-f0ee-48f1-8c2b-c60b97781816" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsScheduleofSeniorNotesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsScheduleofSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsScheduleofSeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_bb730925-3106-4bfb-8e09-329c0eee6885" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_DebtInstrumentTable_bb730925-3106-4bfb-8e09-329c0eee6885" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_a77c9005-a08b-4c6f-b2a8-018dd54208af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_bb730925-3106-4bfb-8e09-329c0eee6885" xlink:to="loc_us-gaap_DebtInstrumentAxis_a77c9005-a08b-4c6f-b2a8-018dd54208af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_a77c9005-a08b-4c6f-b2a8-018dd54208af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_a77c9005-a08b-4c6f-b2a8-018dd54208af" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_a77c9005-a08b-4c6f-b2a8-018dd54208af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_92be9946-5a30-4afe-a017-41a03534f3db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_a77c9005-a08b-4c6f-b2a8-018dd54208af" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_92be9946-5a30-4afe-a017-41a03534f3db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SevenPointEightSevenFivePercentSeniorNotesDueTwoThousandTwentySixMember_d9cbc875-2d5b-4e32-b51c-23809fb29179" xlink:href="onit-20240930.xsd#onit_SevenPointEightSevenFivePercentSeniorNotesDueTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_92be9946-5a30-4afe-a017-41a03534f3db" xlink:to="loc_onit_SevenPointEightSevenFivePercentSeniorNotesDueTwoThousandTwentySixMember_d9cbc875-2d5b-4e32-b51c-23809fb29179" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TwelvePercentPaidInCashOrThirteenPointTwoFivePercentPaidInKindSeniorNotesDueTwoThousandTwentySevenMember_d54ccc2e-f7ea-49a7-85fb-247734c6f47e" xlink:href="onit-20240930.xsd#onit_TwelvePercentPaidInCashOrThirteenPointTwoFivePercentPaidInKindSeniorNotesDueTwoThousandTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_92be9946-5a30-4afe-a017-41a03534f3db" xlink:to="loc_onit_TwelvePercentPaidInCashOrThirteenPointTwoFivePercentPaidInKindSeniorNotesDueTwoThousandTwentySevenMember_d54ccc2e-f7ea-49a7-85fb-247734c6f47e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ce522f5d-e9de-4f22-9efb-4524fa0e604a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_bb730925-3106-4bfb-8e09-329c0eee6885" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ce522f5d-e9de-4f22-9efb-4524fa0e604a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ce522f5d-e9de-4f22-9efb-4524fa0e604a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ce522f5d-e9de-4f22-9efb-4524fa0e604a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ce522f5d-e9de-4f22-9efb-4524fa0e604a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2e3e1933-2b66-4c5d-9b8b-f327a9896755" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ce522f5d-e9de-4f22-9efb-4524fa0e604a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2e3e1933-2b66-4c5d-9b8b-f327a9896755" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_80e8be7a-45b3-48de-afeb-a222a46decd7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2e3e1933-2b66-4c5d-9b8b-f327a9896755" xlink:to="loc_us-gaap_SecuredDebtMember_80e8be7a-45b3-48de-afeb-a222a46decd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentInKindPIKNoteMember_64c56b60-12dd-4d13-94c1-6ee263c1f75c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentInKindPIKNoteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2e3e1933-2b66-4c5d-9b8b-f327a9896755" xlink:to="loc_us-gaap_PaymentInKindPIKNoteMember_64c56b60-12dd-4d13-94c1-6ee263c1f75c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_00a1b76a-c968-4a47-96b9-0747fe037615" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2e3e1933-2b66-4c5d-9b8b-f327a9896755" xlink:to="loc_us-gaap_SeniorNotesMember_00a1b76a-c968-4a47-96b9-0747fe037615" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_94cc7889-660e-4219-b7c3-33607b77d1b3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_bb730925-3106-4bfb-8e09-329c0eee6885" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_94cc7889-660e-4219-b7c3-33607b77d1b3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_94cc7889-660e-4219-b7c3-33607b77d1b3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_94cc7889-660e-4219-b7c3-33607b77d1b3" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_94cc7889-660e-4219-b7c3-33607b77d1b3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_1f3f452e-d310-4af0-8a33-dc77a9a3f9cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_94cc7889-660e-4219-b7c3-33607b77d1b3" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_1f3f452e-d310-4af0-8a33-dc77a9a3f9cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_2008d603-86c3-4741-b9ef-4b2d60527cd4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_1f3f452e-d310-4af0-8a33-dc77a9a3f9cd" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodTwoMember_2008d603-86c3-4741-b9ef-4b2d60527cd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a22fef88-37d9-4c10-bfad-609435340c59" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_a22fef88-37d9-4c10-bfad-609435340c59" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorLongTermNotes_f027a703-287d-4724-9f21-e1075cf357c5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorLongTermNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_SeniorLongTermNotes_f027a703-287d-4724-9f21-e1075cf357c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_488f55fe-b758-434f-86c4-d8954bf41378" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_488f55fe-b758-434f-86c4-d8954bf41378" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_95103103-2072-4fef-a759-c8954d3f76ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_95103103-2072-4fef-a759-c8954d3f76ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_9efb4373-96a7-4c26-b88f-858b615e4182" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_9efb4373-96a7-4c26-b88f-858b615e4182" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_9228287b-0661-420c-a85a-b934cb0646bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_SeniorNotes_9228287b-0661-420c-a85a-b934cb0646bc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_7780b25d-9df1-4767-9021-d3f47a2303ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5c9b8771-48a5-46b3-b66a-a584ff381af6" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentage_7780b25d-9df1-4767-9021-d3f47a2303ed" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9841dca5-175f-4cc4-9f3e-87bf7582d6c2" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:to="loc_srt_RangeAxis_9841dca5-175f-4cc4-9f3e-87bf7582d6c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9841dca5-175f-4cc4-9f3e-87bf7582d6c2_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9841dca5-175f-4cc4-9f3e-87bf7582d6c2" xlink:to="loc_srt_RangeMember_9841dca5-175f-4cc4-9f3e-87bf7582d6c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9d3a7c30-fe78-4e26-8cdb-663c4f7223ed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9841dca5-175f-4cc4-9f3e-87bf7582d6c2" xlink:to="loc_srt_RangeMember_9d3a7c30-fe78-4e26-8cdb-663c4f7223ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_8844c8c0-5293-4661-9db5-fc17d238ccc5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9d3a7c30-fe78-4e26-8cdb-663c4f7223ed" xlink:to="loc_srt_MinimumMember_8844c8c0-5293-4661-9db5-fc17d238ccc5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_e3f71e74-f514-446f-8020-aeca35535fbb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:to="loc_us-gaap_DebtInstrumentAxis_e3f71e74-f514-446f-8020-aeca35535fbb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e3f71e74-f514-446f-8020-aeca35535fbb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_e3f71e74-f514-446f-8020-aeca35535fbb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e3f71e74-f514-446f-8020-aeca35535fbb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7606c435-79ac-4a4d-b264-f2da494c3e25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_e3f71e74-f514-446f-8020-aeca35535fbb" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7606c435-79ac-4a4d-b264-f2da494c3e25" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PMCSeniorSecuredNotesMember_c60acb8d-eb6f-45f8-a828-c2465ad1d72a" xlink:href="onit-20240930.xsd#onit_PMCSeniorSecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7606c435-79ac-4a4d-b264-f2da494c3e25" xlink:to="loc_onit_PMCSeniorSecuredNotesMember_c60acb8d-eb6f-45f8-a828-c2465ad1d72a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SeniorNotesDue2029Member_cfcd1b74-119c-413b-a2e4-3c382f1deb36" xlink:href="onit-20240930.xsd#onit_SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7606c435-79ac-4a4d-b264-f2da494c3e25" xlink:to="loc_onit_SeniorNotesDue2029Member_cfcd1b74-119c-413b-a2e4-3c382f1deb36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_faddc1ca-4438-44b6-b0c8-91f14627164b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_faddc1ca-4438-44b6-b0c8-91f14627164b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_faddc1ca-4438-44b6-b0c8-91f14627164b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_faddc1ca-4438-44b6-b0c8-91f14627164b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_faddc1ca-4438-44b6-b0c8-91f14627164b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_63e3ff2c-ed87-4687-8206-24081bf7bfe0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_faddc1ca-4438-44b6-b0c8-91f14627164b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_63e3ff2c-ed87-4687-8206-24081bf7bfe0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_a3428390-7c95-4d28-8001-21023c50c534" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_63e3ff2c-ed87-4687-8206-24081bf7bfe0" xlink:to="loc_us-gaap_SubsequentEventMember_a3428390-7c95-4d28-8001-21023c50c534" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingMoodysAxis_f72feaee-4202-4933-ac97-d3cfe3b1c5be" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CreditRatingMoodysAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:to="loc_srt_CreditRatingMoodysAxis_f72feaee-4202-4933-ac97-d3cfe3b1c5be" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingMoodysMember_f72feaee-4202-4933-ac97-d3cfe3b1c5be_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExternalCreditRatingMoodysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingMoodysAxis_f72feaee-4202-4933-ac97-d3cfe3b1c5be" xlink:to="loc_srt_ExternalCreditRatingMoodysMember_f72feaee-4202-4933-ac97-d3cfe3b1c5be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingMoodysMember_cea6ef24-eb63-4d83-8ba6-785ce9f1b454" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExternalCreditRatingMoodysMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingMoodysAxis_f72feaee-4202-4933-ac97-d3cfe3b1c5be" xlink:to="loc_srt_ExternalCreditRatingMoodysMember_cea6ef24-eb63-4d83-8ba6-785ce9f1b454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MoodysCaa1RatingMember_3babc286-0594-4666-81fd-e6e0fd5f147e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MoodysCaa1RatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingMoodysMember_cea6ef24-eb63-4d83-8ba6-785ce9f1b454" xlink:to="loc_srt_MoodysCaa1RatingMember_3babc286-0594-4666-81fd-e6e0fd5f147e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CreditRatingStandardPoorsAxis_e6f12d14-8efe-4714-83bc-48244cfb12cb" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CreditRatingStandardPoorsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_68deabc9-e83c-4a23-8925-ecaa0c5c40b5" xlink:to="loc_srt_CreditRatingStandardPoorsAxis_e6f12d14-8efe-4714-83bc-48244cfb12cb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingStandardPoorsMember_e6f12d14-8efe-4714-83bc-48244cfb12cb_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExternalCreditRatingStandardPoorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CreditRatingStandardPoorsAxis_e6f12d14-8efe-4714-83bc-48244cfb12cb" xlink:to="loc_srt_ExternalCreditRatingStandardPoorsMember_e6f12d14-8efe-4714-83bc-48244cfb12cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExternalCreditRatingStandardPoorsMember_72b2b846-248f-4265-9cf6-aa9f58707162" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ExternalCreditRatingStandardPoorsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CreditRatingStandardPoorsAxis_e6f12d14-8efe-4714-83bc-48244cfb12cb" xlink:to="loc_srt_ExternalCreditRatingStandardPoorsMember_72b2b846-248f-4265-9cf6-aa9f58707162" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StandardPoorsBMinusRatingMember_5d42d73f-a97e-4258-8a0a-f5debd7279d5" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StandardPoorsBMinusRatingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ExternalCreditRatingStandardPoorsMember_72b2b846-248f-4265-9cf6-aa9f58707162" xlink:to="loc_srt_StandardPoorsBMinusRatingMember_5d42d73f-a97e-4258-8a0a-f5debd7279d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtInstrumentCovenantComplianceConsolidatedTangibleNetWorthatPeriodEnd_ea27a424-7061-47a9-945e-ac120d67c61c" xlink:href="onit-20240930.xsd#onit_DebtInstrumentCovenantComplianceConsolidatedTangibleNetWorthatPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_onit_DebtInstrumentCovenantComplianceConsolidatedTangibleNetWorthatPeriodEnd_ea27a424-7061-47a9-945e-ac120d67c61c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtInstrumentCovenantComplianceLiquidityRequirement_522f7b54-a9e3-49b5-b382-52a9c7feeab5" xlink:href="onit-20240930.xsd#onit_DebtInstrumentCovenantComplianceLiquidityRequirement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_onit_DebtInstrumentCovenantComplianceLiquidityRequirement_522f7b54-a9e3-49b5-b382-52a9c7feeab5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_c65b680f-98de-4b4d-ac46-3993531b9096" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_c65b680f-98de-4b4d-ac46-3993531b9096" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchaseAmount_b64c6a33-e29b-4f90-8ab3-f29b0775af0d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentRepurchaseAmount_b64c6a33-e29b-4f90-8ab3-f29b0775af0d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_f8ce9253-0f10-4369-a7d1-880c27ff7c1d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_f8ce9253-0f10-4369-a7d1-880c27ff7c1d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_06842a13-96d6-4609-8c8d-fc9b43a37ac6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_06842a13-96d6-4609-8c8d-fc9b43a37ac6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_53186941-46a0-4885-9f68-7c39961c713c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_53186941-46a0-4885-9f68-7c39961c713c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_aeca1bed-d928-4c68-9177-751879d6f7cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7884dc6d-0621-46ca-b1a6-c8cd026578d2" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_aeca1bed-d928-4c68-9177-751879d6f7cb" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsScheduleofAssetsHeldasCollateralRelatedtoSecuredBorrowingsDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsScheduleofAssetsHeldasCollateralRelatedtoSecuredBorrowingsDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsScheduleofAssetsHeldasCollateralRelatedtoSecuredBorrowingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_53744567-1968-47fe-8a26-a1666f8cb24d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_DebtInstrumentTable_53744567-1968-47fe-8a26-a1666f8cb24d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryAxis_c07f4d38-666f-4b5c-82af-5221f2117fe2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_53744567-1968-47fe-8a26-a1666f8cb24d" xlink:to="loc_us-gaap_LienCategoryAxis_c07f4d38-666f-4b5c-82af-5221f2117fe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_c07f4d38-666f-4b5c-82af-5221f2117fe2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LienCategoryAxis_c07f4d38-666f-4b5c-82af-5221f2117fe2" xlink:to="loc_us-gaap_LienCategoryDomain_c07f4d38-666f-4b5c-82af-5221f2117fe2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LienCategoryAxis_c07f4d38-666f-4b5c-82af-5221f2117fe2" xlink:to="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsMember_02ffbb58-baa1-486d-ab29-6b2f5b5c48b9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:to="loc_us-gaap_AssetsMember_02ffbb58-baa1-486d-ab29-6b2f5b5c48b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralMember_fffe018f-9bb3-492c-9154-88027699b75c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:to="loc_us-gaap_AssetPledgedAsCollateralMember_fffe018f-9bb3-492c-9154-88027699b75c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollateralizedDebtObligationsMember_9ae7e10d-ea76-4af5-9892-98c47ec6f5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollateralizedDebtObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:to="loc_us-gaap_CollateralizedDebtObligationsMember_9ae7e10d-ea76-4af5-9892-98c47ec6f5a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorLienMember_52234003-2485-4d54-9538-88a5c50f5acb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorLienMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:to="loc_us-gaap_SeniorLienMember_52234003-2485-4d54-9538-88a5c50f5acb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnencumberedAssetsMember_55130399-002d-44b7-b98e-0b316a00366d" xlink:href="onit-20240930.xsd#onit_UnencumberedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_c790b93b-0245-47d6-bde8-c7ee7fe28f7f" xlink:to="loc_onit_UnencumberedAssetsMember_55130399-002d-44b7-b98e-0b316a00366d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusAxis_768faa3b-8ce9-4edd-8841-d3015d7d3345" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_53744567-1968-47fe-8a26-a1666f8cb24d" xlink:to="loc_us-gaap_PledgedStatusAxis_768faa3b-8ce9-4edd-8841-d3015d7d3345" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_768faa3b-8ce9-4edd-8841-d3015d7d3345_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PledgedStatusAxis_768faa3b-8ce9-4edd-8841-d3015d7d3345" xlink:to="loc_us-gaap_PledgedStatusDomain_768faa3b-8ce9-4edd-8841-d3015d7d3345_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PledgedStatusDomain_316c051f-1664-47da-b792-c2e640b89283" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PledgedStatusAxis_768faa3b-8ce9-4edd-8841-d3015d7d3345" xlink:to="loc_us-gaap_PledgedStatusDomain_316c051f-1664-47da-b792-c2e640b89283" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_ed707e4e-f301-48c0-a3b8-163040f46937" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralWithRightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PledgedStatusDomain_316c051f-1664-47da-b792-c2e640b89283" xlink:to="loc_us-gaap_AssetPledgedAsCollateralWithRightMember_ed707e4e-f301-48c0-a3b8-163040f46937" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_dc0b516b-8458-4e0d-91ac-92502b195ff0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_Cash_dc0b516b-8458-4e0d-91ac-92502b195ff0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalents_1895c6dd-51bf-4ddd-9eae-212b5c163019" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalents_1895c6dd-51bf-4ddd-9eae-212b5c163019" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_feaa3976-d748-44cc-bdd8-6e7c3e1d463d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_feaa3976-d748-44cc-bdd8-6e7c3e1d463d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableFairValueDisclosure_cd7b26a5-b2bb-44bb-b6a4-862eb958a256" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansReceivableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_LoansReceivableFairValueDisclosure_cd7b26a5-b2bb-44bb-b6a4-862eb958a256" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForInvestmentReverseMortgagesUnSecuritizedLoans_84da1608-82ea-4924-813b-6cfa4bafbe52" xlink:href="onit-20240930.xsd#onit_LoansHeldForInvestmentReverseMortgagesUnSecuritizedLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_onit_LoansHeldForInvestmentReverseMortgagesUnSecuritizedLoans_84da1608-82ea-4924-813b-6cfa4bafbe52" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_61de6520-0b6d-4963-975b-b9c10b2588d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_ServicingAsset_61de6520-0b6d-4963-975b-b9c10b2588d5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_Advances_6e2bed40-2619-49e2-a274-19a5edee1104" xlink:href="onit-20240930.xsd#onit_Advances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_onit_Advances_6e2bed40-2619-49e2-a274-19a5edee1104" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_985384ce-4475-4c5c-912b-ee65edd0fb8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_OtherReceivables_985384ce-4475-4c5c-912b-ee65edd0fb8b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRealEstate_f6d32a1b-70b6-4d32-b4ba-f5a63afde7e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_OtherRealEstate_f6d32a1b-70b6-4d32-b4ba-f5a63afde7e4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_af1b205c-3bf9-4e1a-b8e8-81af9abe1e5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_4266942a-415b-488a-9d81-2926f8109088" xlink:to="loc_us-gaap_Assets_af1b205c-3bf9-4e1a-b8e8-81af9abe1e5a" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BorrowingsScheduleofSecondLienPriorityonSpecifiedAssetsCarriedonBalanceSheetDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BorrowingsScheduleofSecondLienPriorityonSpecifiedAssetsCarriedonBalanceSheetDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BorrowingsScheduleofSecondLienPriorityonSpecifiedAssetsCarriedonBalanceSheetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_cf77818b-c67e-42cd-adab-ed407c9bccd4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_us-gaap_DebtInstrumentTable_cf77818b-c67e-42cd-adab-ed407c9bccd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryAxis_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_cf77818b-c67e-42cd-adab-ed407c9bccd4" xlink:to="loc_us-gaap_LienCategoryAxis_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LienCategoryAxis_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc" xlink:to="loc_us-gaap_LienCategoryDomain_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LienCategoryDomain_6a9062f4-5b34-4e09-b6c9-6ae72c3853a2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LienCategoryDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LienCategoryAxis_1415ae7b-c1ea-4260-b1cb-e8b4efb7efbc" xlink:to="loc_us-gaap_LienCategoryDomain_6a9062f4-5b34-4e09-b6c9-6ae72c3853a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_JuniorLienMember_1718e7c5-21f7-4c32-b9e3-f7d920d4baef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_JuniorLienMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LienCategoryDomain_6a9062f4-5b34-4e09-b6c9-6ae72c3853a2" xlink:to="loc_us-gaap_JuniorLienMember_1718e7c5-21f7-4c32-b9e3-f7d920d4baef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_Advances_de7d7c3e-3e4a-46e2-95f7-8cdb10a83ac0" xlink:href="onit-20240930.xsd#onit_Advances"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_onit_Advances_de7d7c3e-3e4a-46e2-95f7-8cdb10a83ac0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DeferredServicingIncome_94639c28-9648-4ec8-a9df-254e62c5bbed" xlink:href="onit-20240930.xsd#onit_DeferredServicingIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_onit_DeferredServicingIncome_94639c28-9648-4ec8-a9df-254e62c5bbed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_ba89f0a8-5c39-49f9-9faa-60ae8d20e40f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_us-gaap_ServicingAsset_ba89f0a8-5c39-49f9-9faa-60ae8d20e40f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_fce83709-b0a3-478a-8dc3-4ecf2a193f48" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_us-gaap_Cash_fce83709-b0a3-478a-8dc3-4ecf2a193f48" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdvanceFacilityReserve_9da52575-1f5d-42ca-8741-06446f1912ad" xlink:href="onit-20240930.xsd#onit_AdvanceFacilityReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_onit_AdvanceFacilityReserve_9da52575-1f5d-42ca-8741-06446f1912ad" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SpecifiedLoanValue_1da1aa0c-8563-4f9a-bf16-63993b466c98" xlink:href="onit-20240930.xsd#onit_SpecifiedLoanValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_onit_SpecifiedLoanValue_1da1aa0c-8563-4f9a-bf16-63993b466c98" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SpecifiedResidualValue_8ac54534-bb3b-4bdb-8887-256fead17b36" xlink:href="onit-20240930.xsd#onit_SpecifiedResidualValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_onit_SpecifiedResidualValue_8ac54534-bb3b-4bdb-8887-256fead17b36" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_71969b8e-3ac5-4616-8380-83d8e800e215" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_eb96986d-eef2-44c7-a1b6-3f6ca1735f44" xlink:to="loc_us-gaap_Assets_71969b8e-3ac5-4616-8380-83d8e800e215" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesSummaryofDerivativesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#DerivativeFinancialInstrumentsandHedgingActivitiesSummaryofDerivativesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesSummaryofDerivativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_1ee2de33-419c-4584-b485-75623da971da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeTable_1ee2de33-419c-4584-b485-75623da971da" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_df11cf1d-144c-4a64-868f-18024aa15bde" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_1ee2de33-419c-4584-b485-75623da971da" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_df11cf1d-144c-4a64-868f-18024aa15bde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_df11cf1d-144c-4a64-868f-18024aa15bde_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_df11cf1d-144c-4a64-868f-18024aa15bde" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_df11cf1d-144c-4a64-868f-18024aa15bde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_df11cf1d-144c-4a64-868f-18024aa15bde" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardSalesOfReverseLoansMember_2c9930c2-712d-44d6-bbc8-690454170abd" xlink:href="onit-20240930.xsd#onit_ForwardSalesOfReverseLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_ForwardSalesOfReverseLoansMember_2c9930c2-712d-44d6-bbc8-690454170abd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_b9de42ab-0915-499a-9c9c-0d59493cc033" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_b9de42ab-0915-499a-9c9c-0d59493cc033" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ReverseMortgageLoanInterestRateLockCommitmentsMember_864ee3b3-0ec0-4e03-8bbd-98d365fe3ee8" xlink:href="onit-20240930.xsd#onit_ReverseMortgageLoanInterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_ReverseMortgageLoanInterestRateLockCommitmentsMember_864ee3b3-0ec0-4e03-8bbd-98d365fe3ee8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TBAForwardMortgageBackedSecuritiesTradesMember_94979e15-0f25-44a4-9ad5-8de5f8fb1f80" xlink:href="onit-20240930.xsd#onit_TBAForwardMortgageBackedSecuritiesTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_TBAForwardMortgageBackedSecuritiesTradesMember_94979e15-0f25-44a4-9ad5-8de5f8fb1f80" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_62892c36-c5e9-4d48-9cba-431fc0231114" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_us-gaap_InterestRateSwapMember_62892c36-c5e9-4d48-9cba-431fc0231114" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OptionOnSecuritiesMember_242a428b-5efe-4953-866a-32b0974f7ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionOnSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_us-gaap_OptionOnSecuritiesMember_242a428b-5efe-4953-866a-32b0974f7ac4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TBAForwardPipelinesTradesMember_9eecc196-4ad7-46a3-b515-eb218000a4e6" xlink:href="onit-20240930.xsd#onit_TBAForwardPipelinesTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_TBAForwardPipelinesTradesMember_9eecc196-4ad7-46a3-b515-eb218000a4e6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InterestRateSwapFuturesAndTBAForwardMBSTradesMember_d2c40ad8-ed8e-42b1-895e-3279d03514da" xlink:href="onit-20240930.xsd#onit_InterestRateSwapFuturesAndTBAForwardMBSTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_InterestRateSwapFuturesAndTBAForwardMBSTradesMember_d2c40ad8-ed8e-42b1-895e-3279d03514da" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMember_1e6f9e1a-3971-4304-bb61-e7f351d6956b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_us-gaap_DerivativeMember_1e6f9e1a-3971-4304-bb61-e7f351d6956b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherDerivativesMember_893a9dc5-8d24-4a78-876b-3ba031d9f0be" xlink:href="onit-20240930.xsd#onit_OtherDerivativesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_OtherDerivativesMember_893a9dc5-8d24-4a78-876b-3ba031d9f0be" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardTradesMember_e74e5fce-1494-40fe-88dd-04fe6ce15ef0" xlink:href="onit-20240930.xsd#onit_ForwardTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_ForwardTradesMember_e74e5fce-1494-40fe-88dd-04fe6ce15ef0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardLHFSTradesMember_173ffa11-444a-48dc-aa12-5111b708c3c5" xlink:href="onit-20240930.xsd#onit_ForwardLHFSTradesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_08b68074-0ed1-4c29-9508-7952dd042a7b" xlink:to="loc_onit_ForwardLHFSTradesMember_173ffa11-444a-48dc-aa12-5111b708c3c5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_b4c51411-86f9-4f80-905a-3a0652d72727" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeNotionalAmount_b4c51411-86f9-4f80-905a-3a0652d72727" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_deacee8a-6501-445f-933d-32f9b478c12a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_deacee8a-6501-445f-933d-32f9b478c12a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_0c3f92ab-1124-4031-a004-aa794e4d28b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_0c3f92ab-1124-4031-a004-aa794e4d28b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_01573ee7-af46-4bec-8785-8e0d089a00fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_01573ee7-af46-4bec-8785-8e0d089a00fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_989d64cf-dd6b-4857-b8e1-af62e4223572" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_870cce44-0ef8-42c2-9de6-b87aa209391c" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_989d64cf-dd6b-4857-b8e1-af62e4223572" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/DerivativeFinancialInstrumentsandHedgingActivitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_2e475856-ecde-4a5a-b1a3-50e672e75324" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_us-gaap_DerivativeTable_2e475856-ecde-4a5a-b1a3-50e672e75324" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_1c9f7a49-a80e-43ae-9c35-0299922aa98c" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_2e475856-ecde-4a5a-b1a3-50e672e75324" xlink:to="loc_srt_RangeAxis_1c9f7a49-a80e-43ae-9c35-0299922aa98c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_1c9f7a49-a80e-43ae-9c35-0299922aa98c_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1c9f7a49-a80e-43ae-9c35-0299922aa98c" xlink:to="loc_srt_RangeMember_1c9f7a49-a80e-43ae-9c35-0299922aa98c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ae437b5a-1985-43f9-85fa-33f8e30df5ec" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1c9f7a49-a80e-43ae-9c35-0299922aa98c" xlink:to="loc_srt_RangeMember_ae437b5a-1985-43f9-85fa-33f8e30df5ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_66db6eb8-d1db-44ee-b210-5aa3f68e0cc1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ae437b5a-1985-43f9-85fa-33f8e30df5ec" xlink:to="loc_srt_MinimumMember_66db6eb8-d1db-44ee-b210-5aa3f68e0cc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_dcd83637-2c96-4896-8105-a3dd1ea6ac7a" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_ae437b5a-1985-43f9-85fa-33f8e30df5ec" xlink:to="loc_srt_MaximumMember_dcd83637-2c96-4896-8105-a3dd1ea6ac7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_2e475856-ecde-4a5a-b1a3-50e672e75324" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4caa4947-d3e0-4c7d-b126-90e9f328a59f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_bcfb9b2d-6c97-455c-acbf-e3a7c015bf85" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4caa4947-d3e0-4c7d-b126-90e9f328a59f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_07c1f7e3-9471-409e-9f3e-40f58fd50510" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4caa4947-d3e0-4c7d-b126-90e9f328a59f" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_07c1f7e3-9471-409e-9f3e-40f58fd50510" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanCommitmentTerm_80e961fe-2e0a-40de-a48b-ff00c9c12f74" xlink:href="onit-20240930.xsd#onit_LoanCommitmentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_LoanCommitmentTerm_80e961fe-2e0a-40de-a48b-ff00c9c12f74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanCommitmentAverageTerm_a4f7a040-54bb-4422-ab6b-35e193ba841c" xlink:href="onit-20240930.xsd#onit_LoanCommitmentAverageTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_LoanCommitmentAverageTerm_a4f7a040-54bb-4422-ab6b-35e193ba841c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoansHeldForSalePeriodOfSale_b0018ae0-04ed-4009-aaf8-fa52961fd79e" xlink:href="onit-20240930.xsd#onit_LoansHeldForSalePeriodOfSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_LoansHeldForSalePeriodOfSale_b0018ae0-04ed-4009-aaf8-fa52961fd79e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanCommitmentToCorrespondents_0c1e0844-dcb6-48a8-af6b-bd04e97bd99d" xlink:href="onit-20240930.xsd#onit_LoanCommitmentToCorrespondents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_LoanCommitmentToCorrespondents_0c1e0844-dcb6-48a8-af6b-bd04e97bd99d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MinimumHedgeCoverageRatio_eafa236e-e92b-4e0a-a179-9a6c2a36832c" xlink:href="onit-20240930.xsd#onit_MinimumHedgeCoverageRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_MinimumHedgeCoverageRatio_eafa236e-e92b-4e0a-a179-9a6c2a36832c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InterestRateRiskChangeInInterestRate_9edee6e0-06fd-433a-8c66-ab5988b6e89c" xlink:href="onit-20240930.xsd#onit_InterestRateRiskChangeInInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_2fcb712a-abd5-4833-93a9-a061753f9adc" xlink:to="loc_onit_InterestRateRiskChangeInInterestRate_9edee6e0-06fd-433a-8c66-ab5988b6e89c" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/InterestExpenseScheduleofComponentsofInterestExpenseDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#InterestExpenseScheduleofComponentsofInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/InterestExpenseScheduleofComponentsofInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_onit_ScheduleofInterestExpenseLineItems_10f0dee7-f509-4bbd-86d7-4bd9d6601e5a" xlink:href="onit-20240930.xsd#onit_ScheduleofInterestExpenseLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ScheduleofInterestExpenseTable_5ca8ab98-3b00-47cb-938c-2cccbbcb45e4" xlink:href="onit-20240930.xsd#onit_ScheduleofInterestExpenseTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_onit_ScheduleofInterestExpenseLineItems_10f0dee7-f509-4bbd-86d7-4bd9d6601e5a" xlink:to="loc_onit_ScheduleofInterestExpenseTable_5ca8ab98-3b00-47cb-938c-2cccbbcb45e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_09ffe6b1-1413-435b-ac55-b245d5d55950" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_onit_ScheduleofInterestExpenseTable_5ca8ab98-3b00-47cb-938c-2cccbbcb45e4" xlink:to="loc_us-gaap_DebtInstrumentAxis_09ffe6b1-1413-435b-ac55-b245d5d55950" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_09ffe6b1-1413-435b-ac55-b245d5d55950_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_09ffe6b1-1413-435b-ac55-b245d5d55950" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_09ffe6b1-1413-435b-ac55-b245d5d55950_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_09ffe6b1-1413-435b-ac55-b245d5d55950" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorSubordinatedNotesMember_61b51c27-4976-478a-be82-b6f4f356ddbd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorSubordinatedNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_us-gaap_SeniorSubordinatedNotesMember_61b51c27-4976-478a-be82-b6f4f356ddbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_507db65c-3b0c-4278-b4b9-7432ce292890" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_us-gaap_SeniorNotesMember_507db65c-3b0c-4278-b4b9-7432ce292890" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MSRFinancingFacilitiesMember_5c687802-2502-4445-b73d-87b748d4323d" xlink:href="onit-20240930.xsd#onit_MSRFinancingFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_onit_MSRFinancingFacilitiesMember_5c687802-2502-4445-b73d-87b748d4323d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarehouseAgreementBorrowingsMember_8df5ba08-334a-4530-ba6f-cfa0b1142564" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WarehouseAgreementBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_us-gaap_WarehouseAgreementBorrowingsMember_8df5ba08-334a-4530-ba6f-cfa0b1142564" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MatchFundedLiabiltiesMember_342191f0-c418-46b0-8727-ba777884d979" xlink:href="onit-20240930.xsd#onit_MatchFundedLiabiltiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_onit_MatchFundedLiabiltiesMember_342191f0-c418-46b0-8727-ba777884d979" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_EscrowMember_640e7b49-2bcf-424e-b2de-36cc1db85ce9" xlink:href="onit-20240930.xsd#onit_EscrowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_096e493b-ae34-47b9-8c09-869d70d7f26e" xlink:to="loc_onit_EscrowMember_640e7b49-2bcf-424e-b2de-36cc1db85ce9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAbstract_e75e2c1e-ad53-47ef-b346-8a79c07a1fda" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ScheduleofInterestExpenseLineItems_10f0dee7-f509-4bbd-86d7-4bd9d6601e5a" xlink:to="loc_us-gaap_DebtSecuritiesAbstract_e75e2c1e-ad53-47ef-b346-8a79c07a1fda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_b523fafd-1e63-4c07-96a5-29db0f781dc6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAbstract_e75e2c1e-ad53-47ef-b346-8a79c07a1fda" xlink:to="loc_us-gaap_InterestExpense_b523fafd-1e63-4c07-96a5-29db0f781dc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_a63dddb3-1799-4e9e-9fc6-a25e46423803" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtSecuritiesAbstract_e75e2c1e-ad53-47ef-b346-8a79c07a1fda" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_a63dddb3-1799-4e9e-9fc6-a25e46423803" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BasicandDilutedEarningsperShareScheduleofReconciliationofCalculationofBasicEarningsperSharetoDilutedEarningsperShareDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BasicandDilutedEarningsperShareScheduleofReconciliationofCalculationofBasicEarningsperSharetoDilutedEarningsperShareDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BasicandDilutedEarningsperShareScheduleofReconciliationofCalculationofBasicEarningsperSharetoDilutedEarningsperShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c64f45a4-c153-4347-893f-b2a78e065d96" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7909b88d-745a-44e5-bab0-2fc7a8bd7270" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c64f45a4-c153-4347-893f-b2a78e065d96" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7909b88d-745a-44e5-bab0-2fc7a8bd7270" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_7909b88d-745a-44e5-bab0-2fc7a8bd7270" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4c2e55de-44d6-4b7f-8d9a-8e1ea5fe7b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1fb05f73-16d1-4ffd-9dcb-32c6f9b72fe8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4c2e55de-44d6-4b7f-8d9a-8e1ea5fe7b5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MarketBasedMember_c2c74f5d-fa62-42a9-8ea7-478238e5e491" xlink:href="onit-20240930.xsd#onit_MarketBasedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_4c2e55de-44d6-4b7f-8d9a-8e1ea5fe7b5b" xlink:to="loc_onit_MarketBasedMember_c2c74f5d-fa62-42a9-8ea7-478238e5e491" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c64f45a4-c153-4347-893f-b2a78e065d96" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_17fc6b72-e0b4-4683-a804-1c1c26acd090" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_NetIncomeLoss_17fc6b72-e0b4-4683-a804-1c1c26acd090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_86ece1c5-2ac9-4d09-a0dd-47a82eeab15d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_86ece1c5-2ac9-4d09-a0dd-47a82eeab15d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_40507068-1bb7-48c1-ad90-8753b0c21a7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_EarningsPerShareBasic_40507068-1bb7-48c1-ad90-8753b0c21a7c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants_91fa21c9-5ee8-4a4c-92a1-75eddc231039" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToCallOptionsAndWarrants_91fa21c9-5ee8-4a4c-92a1-75eddc231039" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_IncrementalCommonSharesAttributableToCommonStockAwards_323124e9-73ce-4ff5-adba-64946167a126" xlink:href="onit-20240930.xsd#onit_IncrementalCommonSharesAttributableToCommonStockAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_onit_IncrementalCommonSharesAttributableToCommonStockAwards_323124e9-73ce-4ff5-adba-64946167a126" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_976ff26c-ad24-4c33-873f-5bdde8d5ce0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_976ff26c-ad24-4c33-873f-5bdde8d5ce0f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_2ecb7317-1282-45a3-84af-6be473d5d50b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_403b1037-d840-45b6-a2ea-c4d09b52f9c3" xlink:to="loc_us-gaap_EarningsPerShareDiluted_2ecb7317-1282-45a3-84af-6be473d5d50b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DilutiveSecuritiesAbstract_615a2464-a77b-435c-92bc-01e1716e2b65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DilutiveSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_c64f45a4-c153-4347-893f-b2a78e065d96" xlink:to="loc_us-gaap_DilutiveSecuritiesAbstract_615a2464-a77b-435c-92bc-01e1716e2b65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_d0970485-5ea1-4ba9-98d9-e7215a3e44db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DilutiveSecuritiesAbstract_615a2464-a77b-435c-92bc-01e1716e2b65" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_d0970485-5ea1-4ba9-98d9-e7215a3e44db" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BusinessSegmentReportingNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BusinessSegmentReportingNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BusinessSegmentReportingNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_eeb6665a-1d74-4de4-bed8-2e38cc743d4e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e32c06c9-48c8-48fa-8d79-7076f181c2fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eeb6665a-1d74-4de4-bed8-2e38cc743d4e" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e32c06c9-48c8-48fa-8d79-7076f181c2fe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e32c06c9-48c8-48fa-8d79-7076f181c2fe" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1" xlink:to="loc_us-gaap_SegmentDomain_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f6fa67bd-8cc1-407c-833b-b0d20cb2a4fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fd6fa35a-f54a-4bc1-b9b1-89be1971c0f1" xlink:to="loc_us-gaap_SegmentDomain_f6fa67bd-8cc1-407c-833b-b0d20cb2a4fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingMember_b1a682c6-9beb-4d63-98b5-11d16e07a23c" xlink:href="onit-20240930.xsd#onit_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f6fa67bd-8cc1-407c-833b-b0d20cb2a4fe" xlink:to="loc_onit_ServicingMember_b1a682c6-9beb-4d63-98b5-11d16e07a23c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginationsMember_64ae8f95-6c67-4ceb-b0ad-454b2ff0fa1b" xlink:href="onit-20240930.xsd#onit_OriginationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f6fa67bd-8cc1-407c-833b-b0d20cb2a4fe" xlink:to="loc_onit_OriginationsMember_64ae8f95-6c67-4ceb-b0ad-454b2ff0fa1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_3d15f9b8-2a05-4245-98a4-a2c894d90745" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eeb6665a-1d74-4de4-bed8-2e38cc743d4e" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_3d15f9b8-2a05-4245-98a4-a2c894d90745" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_fc1cafeb-271c-4a74-b01a-f3dbb5e9441e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eeb6665a-1d74-4de4-bed8-2e38cc743d4e" xlink:to="loc_us-gaap_InterestExpense_fc1cafeb-271c-4a74-b01a-f3dbb5e9441e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BusinessSegmentReportingScheduleofSegmentReportingInformationDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BusinessSegmentReportingScheduleofSegmentReportingInformationDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BusinessSegmentReportingScheduleofSegmentReportingInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_0a0d49d1-3acf-4af7-940c-aefb0464ded0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_c83c0255-06de-4711-8a55-ea79556e8da6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0a0d49d1-3acf-4af7-940c-aefb0464ded0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_c83c0255-06de-4711-8a55-ea79556e8da6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_f9d6878c-044f-4429-8063-5770fe05017e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_c83c0255-06de-4711-8a55-ea79556e8da6" xlink:to="loc_srt_ConsolidationItemsAxis_f9d6878c-044f-4429-8063-5770fe05017e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_f9d6878c-044f-4429-8063-5770fe05017e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_f9d6878c-044f-4429-8063-5770fe05017e" xlink:to="loc_srt_ConsolidationItemsDomain_f9d6878c-044f-4429-8063-5770fe05017e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_98439ed4-5b63-4851-ba26-ce21c6e19487" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_f9d6878c-044f-4429-8063-5770fe05017e" xlink:to="loc_srt_ConsolidationItemsDomain_98439ed4-5b63-4851-ba26-ce21c6e19487" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_d304f010-c552-4751-84b0-beed56378c65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_98439ed4-5b63-4851-ba26-ce21c6e19487" xlink:to="loc_us-gaap_OperatingSegmentsMember_d304f010-c552-4751-84b0-beed56378c65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_c83c0255-06de-4711-8a55-ea79556e8da6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b" xlink:to="loc_us-gaap_SegmentDomain_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_d619a258-f4fc-492b-b790-0ede2c02b832" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_f1d0d116-a659-4718-8e1e-c22f6ac7cd4b" xlink:to="loc_us-gaap_SegmentDomain_d619a258-f4fc-492b-b790-0ede2c02b832" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingMember_92c8293d-323f-4c8f-bb7c-8b8c896d9306" xlink:href="onit-20240930.xsd#onit_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d619a258-f4fc-492b-b790-0ede2c02b832" xlink:to="loc_onit_ServicingMember_92c8293d-323f-4c8f-bb7c-8b8c896d9306" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginationsMember_d1febe96-8ff6-4037-a1f8-b04205c7ed92" xlink:href="onit-20240930.xsd#onit_OriginationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d619a258-f4fc-492b-b790-0ede2c02b832" xlink:to="loc_onit_OriginationsMember_d1febe96-8ff6-4037-a1f8-b04205c7ed92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateAndOtherMember_d021bbdf-f4c5-4503-a273-ecce30c5f41b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_d619a258-f4fc-492b-b790-0ede2c02b832" xlink:to="loc_us-gaap_CorporateAndOtherMember_d021bbdf-f4c5-4503-a273-ecce30c5f41b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:href="onit-20240930.xsd#onit_ResultsOfOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0a0d49d1-3acf-4af7-940c-aefb0464ded0" xlink:to="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFees_2b3d90ad-7997-4edb-b3c3-e857fbfc896c" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_ServicingAndSubservicingFees_2b3d90ad-7997-4edb-b3c3-e857fbfc896c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FeeandCommissionsReverseMortgageBanking_10219d4c-8158-4ed3-9a76-817ac02425a8" xlink:href="onit-20240930.xsd#onit_FeeandCommissionsReverseMortgageBanking"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_FeeandCommissionsReverseMortgageBanking_10219d4c-8158-4ed3-9a76-817ac02425a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSalesOfLoansNet_e468d9af-1ed2-4ad4-a748-2d55f994b886" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSalesOfLoansNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_GainLossOnSalesOfLoansNet_e468d9af-1ed2-4ad4-a748-2d55f994b886" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_be2c9305-0e26-4f78-ad9a-73bffcd33837" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_be2c9305-0e26-4f78-ad9a-73bffcd33837" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_fcf6b78a-7911-4350-b2fc-37f9d4e44b1e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_Revenues_fcf6b78a-7911-4350-b2fc-37f9d4e44b1e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_8310a6e5-99f6-403a-b3de-fe94d5ee53e4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_ServicingAssetAtFairValueChangesInFairValueResultingFromChangesInValuationInputs_8310a6e5-99f6-403a-b3de-fe94d5ee53e4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_c2babb1d-2264-41eb-a9fa-73b47f90d718" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_LaborAndRelatedExpense_c2babb1d-2264-41eb-a9fa-73b47f90d718" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndOrigination_833566ec-1192-46b8-b1cf-ad406edc2490" xlink:href="onit-20240930.xsd#onit_ServicingAndOrigination"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_ServicingAndOrigination_833566ec-1192-46b8-b1cf-ad406edc2490" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommunicationsAndInformationTechnology_ed70fa7b-29d7-46af-8d25-831da39b8b74" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommunicationsAndInformationTechnology"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_CommunicationsAndInformationTechnology_ed70fa7b-29d7-46af-8d25-831da39b8b74" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ProfessionalFeesNet_e4e9b920-fd5b-4866-8e4c-bd2078a5a78b" xlink:href="onit-20240930.xsd#onit_ProfessionalFeesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_ProfessionalFeesNet_e4e9b920-fd5b-4866-8e4c-bd2078a5a78b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_9e7b8dd5-e28e-4134-ba0a-e68843607885" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_ProfessionalFees_9e7b8dd5-e28e-4134-ba0a-e68843607885" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_472f0c0d-580f-470f-bb60-ed1dad7b5113" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OccupancyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_OccupancyNet_472f0c0d-580f-470f-bb60-ed1dad7b5113" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_CorporateOverheadAllocations_f2e45a4a-7937-416c-bd40-82d559d072f7" xlink:href="onit-20240930.xsd#onit_CorporateOverheadAllocations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_CorporateOverheadAllocations_f2e45a4a-7937-416c-bd40-82d559d072f7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherExpenses_85262f23-7f31-4265-bd7b-9326ec9c9f17" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_OtherExpenses_85262f23-7f31-4265-bd7b-9326ec9c9f17" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_d1fa8bd0-ed34-41d8-9926-1d54ab251cba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_us-gaap_CostsAndExpenses_d1fa8bd0-ed34-41d8-9926-1d54ab251cba" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:href="onit-20240930.xsd#onit_OtherIncomeExpenseAbstract0"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_ResultsOfOperationsAbstract_ea079805-679b-4b0b-9ce4-80e69f07fef4" xlink:to="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndOtherIncome_8960671a-573b-4bea-97b7-74ffda945807" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndOtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_InterestAndOtherIncome_8960671a-573b-4bea-97b7-74ffda945807" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_51037166-5482-4fbe-b3d3-27cf86d00813" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_InterestExpense_51037166-5482-4fbe-b3d3-27cf86d00813" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValueAmortization1_fbb9b75e-eb36-49e2-8d47-525ef57d76ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingAssetAtAmortizedValueAmortization1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValueAmortization1_fbb9b75e-eb36-49e2-8d47-525ef57d76ac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_1b307571-6842-4b62-879f-f247c4705ec6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_1b307571-6842-4b62-879f-f247c4705ec6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_7652b38e-c691-4d5d-92c9-afab6a548204" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_7652b38e-c691-4d5d-92c9-afab6a548204" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_de47c39f-41bf-4725-9eb9-ec60d1d0a709" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_de47c39f-41bf-4725-9eb9-ec60d1d0a709" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_10573469-85da-4372-bc6e-87e98ece3168" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_OtherIncomeExpenseAbstract0_d250b292-1d29-4f84-978c-81f8b5f0d422" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_10573469-85da-4372-bc6e-87e98ece3168" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_b4cc7cc7-5ac4-4762-8c6c-67ccf8a90128" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0a0d49d1-3acf-4af7-940c-aefb0464ded0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_b4cc7cc7-5ac4-4762-8c6c-67ccf8a90128" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TotalAssetsAbstract_3355315d-facf-4a20-945c-88310c1d3ecd" xlink:href="onit-20240930.xsd#onit_TotalAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_0a0d49d1-3acf-4af7-940c-aefb0464ded0" xlink:to="loc_onit_TotalAssetsAbstract_3355315d-facf-4a20-945c-88310c1d3ecd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_88409400-64ab-45e7-a7e9-9aed46a4ebd3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_TotalAssetsAbstract_3355315d-facf-4a20-945c-88310c1d3ecd" xlink:to="loc_us-gaap_Assets_88409400-64ab-45e7-a7e9-9aed46a4ebd3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/BusinessSegmentReportingScheduleofDepreciationandAmortizationbySegmentDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#BusinessSegmentReportingScheduleofDepreciationandAmortizationbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/BusinessSegmentReportingScheduleofDepreciationandAmortizationbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_eebd98bb-fca7-458c-99d0-d46ac4a3eeed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d66c329d-c89a-420f-8261-4a089f753b10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eebd98bb-fca7-458c-99d0-d46ac4a3eeed" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d66c329d-c89a-420f-8261-4a089f753b10" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_28d004a5-e51f-4162-93aa-750b68d9da62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d66c329d-c89a-420f-8261-4a089f753b10" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_28d004a5-e51f-4162-93aa-750b68d9da62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_28d004a5-e51f-4162-93aa-750b68d9da62_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_28d004a5-e51f-4162-93aa-750b68d9da62" xlink:to="loc_us-gaap_SegmentDomain_28d004a5-e51f-4162-93aa-750b68d9da62_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fef998e0-0382-4212-81db-c927ff67e7af" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_28d004a5-e51f-4162-93aa-750b68d9da62" xlink:to="loc_us-gaap_SegmentDomain_fef998e0-0382-4212-81db-c927ff67e7af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingMember_85b46a63-bccc-4eab-8e20-d93cb502d9cc" xlink:href="onit-20240930.xsd#onit_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fef998e0-0382-4212-81db-c927ff67e7af" xlink:to="loc_onit_ServicingMember_85b46a63-bccc-4eab-8e20-d93cb502d9cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OriginationsMember_76e671f9-b83b-426c-84d5-c51ab7fc20c7" xlink:href="onit-20240930.xsd#onit_OriginationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fef998e0-0382-4212-81db-c927ff67e7af" xlink:to="loc_onit_OriginationsMember_76e671f9-b83b-426c-84d5-c51ab7fc20c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateAndOtherMember_bba294e2-0721-4ecf-9108-f36b951914fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fef998e0-0382-4212-81db-c927ff67e7af" xlink:to="loc_us-gaap_CorporateAndOtherMember_bba294e2-0721-4ecf-9108-f36b951914fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_9b02aaf9-143a-43e6-93d3-f9855b2d0d20" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_d66c329d-c89a-420f-8261-4a089f753b10" xlink:to="loc_srt_ConsolidationItemsAxis_9b02aaf9-143a-43e6-93d3-f9855b2d0d20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_9b02aaf9-143a-43e6-93d3-f9855b2d0d20_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_9b02aaf9-143a-43e6-93d3-f9855b2d0d20" xlink:to="loc_srt_ConsolidationItemsDomain_9b02aaf9-143a-43e6-93d3-f9855b2d0d20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_c00e124a-2d87-47f4-8220-6d018c5b6e53" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_9b02aaf9-143a-43e6-93d3-f9855b2d0d20" xlink:to="loc_srt_ConsolidationItemsDomain_c00e124a-2d87-47f4-8220-6d018c5b6e53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_eb60a099-a203-40d5-99d2-18ec490f3c75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c00e124a-2d87-47f4-8220-6d018c5b6e53" xlink:to="loc_us-gaap_OperatingSegmentsMember_eb60a099-a203-40d5-99d2-18ec490f3c75" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_df9d0851-8b52-438a-b22c-d79529a9553c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eebd98bb-fca7-458c-99d0-d46ac4a3eeed" xlink:to="loc_us-gaap_AmortizationOfFinancingCostsAndDiscounts_df9d0851-8b52-438a-b22c-d79529a9553c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_15996f38-d8e2-4626-b5e9-e3ae3c6940f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eebd98bb-fca7-458c-99d0-d46ac4a3eeed" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_15996f38-d8e2-4626-b5e9-e3ae3c6940f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_cbdd1ab1-b342-4536-930d-ccbb85e56b79" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_eebd98bb-fca7-458c-99d0-d46ac4a3eeed" xlink:to="loc_us-gaap_Assets_cbdd1ab1-b342-4536-930d-ccbb85e56b79" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/RegulatoryRequirementsNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#RegulatoryRequirementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/RegulatoryRequirementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PublicUtilitiesGeneralDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesGeneralDisclosuresTable_9610253f-824c-49a4-b35a-3c22f3f184c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PublicUtilitiesGeneralDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_us-gaap_PublicUtilitiesGeneralDisclosuresTable_9610253f-824c-49a4-b35a-3c22f3f184c2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_03c0ad26-dea6-4487-b372-a33b9fcc862f" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresTable_9610253f-824c-49a4-b35a-3c22f3f184c2" xlink:to="loc_dei_LegalEntityAxis_03c0ad26-dea6-4487-b372-a33b9fcc862f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_03c0ad26-dea6-4487-b372-a33b9fcc862f_default" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_03c0ad26-dea6-4487-b372-a33b9fcc862f" xlink:to="loc_dei_EntityDomain_03c0ad26-dea6-4487-b372-a33b9fcc862f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5fc95fb6-5ec9-41b5-89f8-9dce4c93a19e" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_03c0ad26-dea6-4487-b372-a33b9fcc862f" xlink:to="loc_dei_EntityDomain_5fc95fb6-5ec9-41b5-89f8-9dce4c93a19e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PHHMortgageCorporationMember_63a22dea-baf7-4e68-9e56-9e5a65b3d31d" xlink:href="onit-20240930.xsd#onit_PHHMortgageCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_5fc95fb6-5ec9-41b5-89f8-9dce4c93a19e" xlink:to="loc_onit_PHHMortgageCorporationMember_63a22dea-baf7-4e68-9e56-9e5a65b3d31d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_a87f1196-7d7d-4cb0-9f23-95097db69bae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresTable_9610253f-824c-49a4-b35a-3c22f3f184c2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_a87f1196-7d7d-4cb0-9f23-95097db69bae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a87f1196-7d7d-4cb0-9f23-95097db69bae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a87f1196-7d7d-4cb0-9f23-95097db69bae" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a87f1196-7d7d-4cb0-9f23-95097db69bae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fc8cde3c-27d9-4c9c-8e9b-e9e5b15009bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_a87f1196-7d7d-4cb0-9f23-95097db69bae" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fc8cde3c-27d9-4c9c-8e9b-e9e5b15009bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OwnedMortgageServicingRightsMember_400ea274-5349-47df-91ac-9d3b09b7d4f8" xlink:href="onit-20240930.xsd#onit_OwnedMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_fc8cde3c-27d9-4c9c-8e9b-e9e5b15009bc" xlink:to="loc_onit_OwnedMortgageServicingRightsMember_400ea274-5349-47df-91ac-9d3b09b7d4f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_45ceccae-3c81-479b-9f80-88742bda25cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresTable_9610253f-824c-49a4-b35a-3c22f3f184c2" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_45ceccae-3c81-479b-9f80-88742bda25cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_45ceccae-3c81-479b-9f80-88742bda25cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_45ceccae-3c81-479b-9f80-88742bda25cc" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_45ceccae-3c81-479b-9f80-88742bda25cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_3e4d0a3b-f464-4ddb-b84a-cf55c1251c88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis_45ceccae-3c81-479b-9f80-88742bda25cc" xlink:to="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_3e4d0a3b-f464-4ddb-b84a-cf55c1251c88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnpaidPrincipalBalanceMember_cc957ec8-50b0-4102-95ed-94f8b149ccfd" xlink:href="onit-20240930.xsd#onit_UnpaidPrincipalBalanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_3e4d0a3b-f464-4ddb-b84a-cf55c1251c88" xlink:to="loc_onit_UnpaidPrincipalBalanceMember_cc957ec8-50b0-4102-95ed-94f8b149ccfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanCountMember_94143233-0661-4343-99fc-6cb9d97262e5" xlink:href="onit-20240930.xsd#onit_LoanCountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesDomain_3e4d0a3b-f464-4ddb-b84a-cf55c1251c88" xlink:to="loc_onit_LoanCountMember_94143233-0661-4343-99fc-6cb9d97262e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalRequiredForCapitalAdequacy_7b402470-676e-4e91-8871-27f9a198d6fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalRequiredForCapitalAdequacy"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_us-gaap_CapitalRequiredForCapitalAdequacy_7b402470-676e-4e91-8871-27f9a198d6fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Capital_0e01d24e-48ed-46b7-9dbe-489e68a650ec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Capital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_us-gaap_Capital_0e01d24e-48ed-46b7-9dbe-489e68a650ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtInstrumentCovenantComplianceLiquidityRequirement_6533feb6-67c8-4251-bf4c-d5eb4af27938" xlink:href="onit-20240930.xsd#onit_DebtInstrumentCovenantComplianceLiquidityRequirement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_onit_DebtInstrumentCovenantComplianceLiquidityRequirement_6533feb6-67c8-4251-bf4c-d5eb4af27938" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Cash_a6c02856-e279-44fa-a80b-9f9d0295cdaa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_us-gaap_Cash_a6c02856-e279-44fa-a80b-9f9d0295cdaa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetsServiced_336b6487-cd85-43a9-8ba8-0ccd7f2ca5b8" xlink:href="onit-20240930.xsd#onit_AssetsServiced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_onit_AssetsServiced_336b6487-cd85-43a9-8ba8-0ccd7f2ca5b8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RegulatoryRequirementEligibleLiquidityForLicensingAndSellerOrServicerObligations_f4c994ad-10c0-49b0-9fa7-b4593317b995" xlink:href="onit-20240930.xsd#onit_RegulatoryRequirementEligibleLiquidityForLicensingAndSellerOrServicerObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PublicUtilitiesGeneralDisclosuresLineItems_563c28bb-2c03-4154-83b7-d499175846bf" xlink:to="loc_onit_RegulatoryRequirementEligibleLiquidityForLicensingAndSellerOrServicerObligations_f4c994ad-10c0-49b0-9fa7-b4593317b995" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/CommitmentsNarrativeDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#CommitmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/CommitmentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_cf242739-038d-4d98-80fa-3256d88ed2fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_cf242739-038d-4d98-80fa-3256d88ed2fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_cf242739-038d-4d98-80fa-3256d88ed2fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_cf242739-038d-4d98-80fa-3256d88ed2fc" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_cf242739-038d-4d98-80fa-3256d88ed2fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_d9f74610-40a0-49e8-9e62-1d3cea6401f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_cf242739-038d-4d98-80fa-3256d88ed2fc" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_d9f74610-40a0-49e8-9e62-1d3cea6401f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_99956807-9dde-4931-9e55-510d185f1443" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_d9f74610-40a0-49e8-9e62-1d3cea6401f3" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_99956807-9dde-4931-9e55-510d185f1443" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_fb444376-485c-4b7b-9b54-90be210585ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_fb444376-485c-4b7b-9b54-90be210585ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_fb444376-485c-4b7b-9b54-90be210585ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_fb444376-485c-4b7b-9b54-90be210585ae" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_fb444376-485c-4b7b-9b54-90be210585ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_fb444376-485c-4b7b-9b54-90be210585ae" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingFeesBenchmarkMember_2d3c5f20-99d5-4332-8d8b-8e7bcf23d607" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingFeesBenchmarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_ServicingAndSubservicingFeesBenchmarkMember_2d3c5f20-99d5-4332-8d8b-8e7bcf23d607" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_UnpaidPrincipalBalanceMember_bf3c8fb6-4366-4505-8788-e796977c896a" xlink:href="onit-20240930.xsd#onit_UnpaidPrincipalBalanceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_UnpaidPrincipalBalanceMember_bf3c8fb6-4366-4505-8788-e796977c896a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanCountMember_ed3e998c-f6d2-4f6e-bf26-45b92fd0faf9" xlink:href="onit-20240930.xsd#onit_LoanCountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_LoanCountMember_ed3e998c-f6d2-4f6e-bf26-45b92fd0faf9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DelinquentLoansMember_8d8874c4-e773-4738-9e4e-984508c92693" xlink:href="onit-20240930.xsd#onit_DelinquentLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_DelinquentLoansMember_8d8874c4-e773-4738-9e4e-984508c92693" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingAndSubservicingPortfolioBenchmarkMember_ae188ea9-443b-4b4d-b9ea-31127a287752" xlink:href="onit-20240930.xsd#onit_ServicingAndSubservicingPortfolioBenchmarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_ServicingAndSubservicingPortfolioBenchmarkMember_ae188ea9-443b-4b4d-b9ea-31127a287752" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PledgedMSRLiabilityExpenseBenchmarkMember_1478dc4f-d089-4a96-a905-e5fa9822025c" xlink:href="onit-20240930.xsd#onit_PledgedMSRLiabilityExpenseBenchmarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b6f76716-acd7-4b8f-b27a-4fdce642749e" xlink:to="loc_onit_PledgedMSRLiabilityExpenseBenchmarkMember_1478dc4f-d089-4a96-a905-e5fa9822025c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_22cbdb9f-a042-4341-826a-6985af41b09b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:to="loc_srt_CounterpartyNameAxis_22cbdb9f-a042-4341-826a-6985af41b09b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_22cbdb9f-a042-4341-826a-6985af41b09b_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_22cbdb9f-a042-4341-826a-6985af41b09b" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_22cbdb9f-a042-4341-826a-6985af41b09b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fb2437ad-0e49-46b5-a82d-07ad17638e3b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_22cbdb9f-a042-4341-826a-6985af41b09b" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fb2437ad-0e49-46b5-a82d-07ad17638e3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_e5e3e969-5f4f-4af1-a439-141b6e3952f6" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fb2437ad-0e49-46b5-a82d-07ad17638e3b" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_e5e3e969-5f4f-4af1-a439-141b6e3952f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpMember_af46d8c8-d193-40e3-b66d-0c185d1a01d1" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fb2437ad-0e49-46b5-a82d-07ad17638e3b" xlink:to="loc_onit_RithmCapitalCorpMember_af46d8c8-d193-40e3-b66d-0c185d1a01d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVAssetVehicleLLCMember_9f300498-6ef6-467b-893c-b7674adab7b2" xlink:href="onit-20240930.xsd#onit_MAVAssetVehicleLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_fb2437ad-0e49-46b5-a82d-07ad17638e3b" xlink:to="loc_onit_MAVAssetVehicleLLCMember_9f300498-6ef6-467b-893c-b7674adab7b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_da95ed15-7fec-414f-8bd5-ef659ea61810" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OtherCommitmentsTable_36be9cfc-55f2-4556-b9fe-79792e7dba3e" xlink:to="loc_us-gaap_FinancialInstrumentAxis_da95ed15-7fec-414f-8bd5-ef659ea61810" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_da95ed15-7fec-414f-8bd5-ef659ea61810_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_da95ed15-7fec-414f-8bd5-ef659ea61810" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_da95ed15-7fec-414f-8bd5-ef659ea61810_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_bae25962-ef94-4560-ae30-3c5ea58fccd9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_da95ed15-7fec-414f-8bd5-ef659ea61810" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_bae25962-ef94-4560-ae30-3c5ea58fccd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FloatingRateReverseMortgageLoansMember_f22f553c-cf03-4d1e-88cf-6ee44bbc0bc2" xlink:href="onit-20240930.xsd#onit_FloatingRateReverseMortgageLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_bae25962-ef94-4560-ae30-3c5ea58fccd9" xlink:to="loc_onit_FloatingRateReverseMortgageLoansMember_f22f553c-cf03-4d1e-88cf-6ee44bbc0bc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ForwardMortgageLoanInterestRateLockCommitmentsMember_8c56495c-2d6c-43a9-af50-e51d6dc7b87c" xlink:href="onit-20240930.xsd#onit_ForwardMortgageLoanInterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_bae25962-ef94-4560-ae30-3c5ea58fccd9" xlink:to="loc_onit_ForwardMortgageLoanInterestRateLockCommitmentsMember_8c56495c-2d6c-43a9-af50-e51d6dc7b87c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ReverseMortgageLoanInterestRateLockCommitmentsMember_67908111-b254-43bd-bef2-423300ffa946" xlink:href="onit-20240930.xsd#onit_ReverseMortgageLoanInterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_bae25962-ef94-4560-ae30-3c5ea58fccd9" xlink:to="loc_onit_ReverseMortgageLoanInterestRateLockCommitmentsMember_67908111-b254-43bd-bef2-423300ffa946" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AdditionalBorrowingCapacityToBorrowers_6c6d1180-89ab-4021-828d-66eb422e361e" xlink:href="onit-20240930.xsd#onit_AdditionalBorrowingCapacityToBorrowers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_onit_AdditionalBorrowingCapacityToBorrowers_6c6d1180-89ab-4021-828d-66eb422e361e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_FundedAmountInConnectionWithReverseMortgageLoans_b5d4fa64-bc38-4a4d-8486-c3cfed199730" xlink:href="onit-20240930.xsd#onit_FundedAmountInConnectionWithReverseMortgageLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_onit_FundedAmountInConnectionWithReverseMortgageLoans_b5d4fa64-bc38-4a4d-8486-c3cfed199730" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ShortTermCommitmentsToLend_a6aa2e65-1a40-440e-87f6-51ac7b5065bf" xlink:href="onit-20240930.xsd#onit_ShortTermCommitmentsToLend"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_onit_ShortTermCommitmentsToLend_a6aa2e65-1a40-440e-87f6-51ac7b5065bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ThresholdPercentageOfOutstandingPrincipalBalanceOnMaximumClaimAmount_cf71a85c-3cef-4ae0-8288-de662fa30423" xlink:href="onit-20240930.xsd#onit_ThresholdPercentageOfOutstandingPrincipalBalanceOnMaximumClaimAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_onit_ThresholdPercentageOfOutstandingPrincipalBalanceOnMaximumClaimAmount_cf71a85c-3cef-4ae0-8288-de662fa30423" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_e0302459-345f-409b-b1f3-0a3ec5e60510" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_e0302459-345f-409b-b1f3-0a3ec5e60510" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ConcentrationRiskAmount_6181ffd7-788b-4b63-9658-24640d25171a" xlink:href="onit-20240930.xsd#onit_ConcentrationRiskAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsLineItems_e8a1227a-edaa-4f8f-9b04-6949e1cc1eca" xlink:to="loc_onit_ConcentrationRiskAmount_6181ffd7-788b-4b63-9658-24640d25171a" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/CommitmentsScheduleofActivityRelatedtoHMBSRepurchasesDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#CommitmentsScheduleofActivityRelatedtoHMBSRepurchasesDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/CommitmentsScheduleofActivityRelatedtoHMBSRepurchasesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentLineItems_7d40df0e-68b6-4258-bd22-8b1b6a47a0ad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentTable_c22ba387-068a-4c2e-9f73-0d487cadc118" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_7d40df0e-68b6-4258-bd22-8b1b6a47a0ad" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentTable_c22ba387-068a-4c2e-9f73-0d487cadc118" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_c22ba387-068a-4c2e-9f73-0d487cadc118" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_df96e9cc-6190-4581-8fa0-317d4896678c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_d43d52c3-ab7d-48a7-9198-0e71e7f81f5a" xlink:to="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_df96e9cc-6190-4581-8fa0-317d4896678c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ActiveMember_9916308c-c6aa-45c8-9407-c98fd0e874c8" xlink:href="onit-20240930.xsd#onit_ActiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_df96e9cc-6190-4581-8fa0-317d4896678c" xlink:to="loc_onit_ActiveMember_9916308c-c6aa-45c8-9407-c98fd0e874c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InactiveMember_ef86b13d-bbe3-4525-83e0-ac412b92d2c7" xlink:href="onit-20240930.xsd#onit_InactiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_df96e9cc-6190-4581-8fa0-317d4896678c" xlink:to="loc_onit_InactiveMember_ef86b13d-bbe3-4525-83e0-ac412b92d2c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountAxis_3c20a7d5-013b-4e7b-9441-673dced1f3d4" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentTable_c22ba387-068a-4c2e-9f73-0d487cadc118" xlink:to="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountAxis_3c20a7d5-013b-4e7b-9441-673dced1f3d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_3c20a7d5-013b-4e7b-9441-673dced1f3d4_default" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountAxis_3c20a7d5-013b-4e7b-9441-673dced1f3d4" xlink:to="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_3c20a7d5-013b-4e7b-9441-673dced1f3d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_48a4ca50-e663-4990-a7d3-99a7bcd62b91" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountAxis_3c20a7d5-013b-4e7b-9441-673dced1f3d4" xlink:to="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_48a4ca50-e663-4990-a7d3-99a7bcd62b91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MaximumClaimAmountLessThan92Member_2d176631-7b95-4ff1-abf2-3b0efbab12bd" xlink:href="onit-20240930.xsd#onit_MaximumClaimAmountLessThan92Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_48a4ca50-e663-4990-a7d3-99a7bcd62b91" xlink:to="loc_onit_MaximumClaimAmountLessThan92Member_2d176631-7b95-4ff1-abf2-3b0efbab12bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MaximumClaimAmountGreaterThan92AndLessThan95Member_4ecf110c-a409-4735-8c94-343b1651fa88" xlink:href="onit-20240930.xsd#onit_MaximumClaimAmountGreaterThan92AndLessThan95Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_48a4ca50-e663-4990-a7d3-99a7bcd62b91" xlink:to="loc_onit_MaximumClaimAmountGreaterThan92AndLessThan95Member_4ecf110c-a409-4735-8c94-343b1651fa88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MaximumClaimAmountGreaterThan95AndLessThan98Member_f0d2738c-9334-4275-bccf-08b40f5445cc" xlink:href="onit-20240930.xsd#onit_MaximumClaimAmountGreaterThan95AndLessThan98Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_HomeEquityConversionMortgageBackedSecurityMaximumClaimAmountDomain_48a4ca50-e663-4990-a7d3-99a7bcd62b91" xlink:to="loc_onit_MaximumClaimAmountGreaterThan95AndLessThan98Member_f0d2738c-9334-4275-bccf-08b40f5445cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SecuritizedHomeEquityConversionMortgageBackedSecurity_2a716678-299e-4722-8f7b-fe60e5acdd83" xlink:href="onit-20240930.xsd#onit_SecuritizedHomeEquityConversionMortgageBackedSecurity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_7d40df0e-68b6-4258-bd22-8b1b6a47a0ad" xlink:to="loc_onit_SecuritizedHomeEquityConversionMortgageBackedSecurity_2a716678-299e-4722-8f7b-fe60e5acdd83" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:href="onit-20240930.xsd#onit_LongTermPurchaseCommitmentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermPurchaseCommitmentLineItems_7d40df0e-68b6-4258-bd22-8b1b6a47a0ad" xlink:to="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecurityRepurchasesOutstandingValue_630d1b95-8017-4b24-95b1-f37089d523e9" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecurityRepurchasesOutstandingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:to="loc_onit_HomeEquityConversionMortgageBackedSecurityRepurchasesOutstandingValue_630d1b95-8017-4b24-95b1-f37089d523e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AmountofAdditionsToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_e568f63f-05a4-4b66-94dd-e1bf50f32386" xlink:href="onit-20240930.xsd#onit_AmountofAdditionsToHomeEquityConversionMortgageBackedSecurityRepurchasesValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:to="loc_onit_AmountofAdditionsToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_e568f63f-05a4-4b66-94dd-e1bf50f32386" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RecoveriesRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_3f887368-3125-4775-98e4-4b685984857b" xlink:href="onit-20240930.xsd#onit_RecoveriesRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:to="loc_onit_RecoveriesRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_3f887368-3125-4775-98e4-4b685984857b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_TransfersRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_450d1da6-9e3c-4b49-8b82-07c14321276f" xlink:href="onit-20240930.xsd#onit_TransfersRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:to="loc_onit_TransfersRelatedToHomeEquityConversionMortgageBackedSecurityRepurchasesValue_450d1da6-9e3c-4b49-8b82-07c14321276f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ChangeInValueOfHomeEquityConversionMortgageBackedSecurityRepurchasesValue_f82884f3-f464-4681-969e-fcf6f3b93782" xlink:href="onit-20240930.xsd#onit_ChangeInValueOfHomeEquityConversionMortgageBackedSecurityRepurchasesValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_onit_LongTermPurchaseCommitmentRollForward_4a1f869e-69d2-4bff-8875-9ee45562716f" xlink:to="loc_onit_ChangeInValueOfHomeEquityConversionMortgageBackedSecurityRepurchasesValue_f82884f3-f464-4681-969e-fcf6f3b93782" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HomeEquityConversionMortgageBackedSecurityRepurchasesOutstandingValue_5771e385-c392-42c9-b93c-5281d36a87d6" xlink:href="onit-20240930.xsd#onit_HomeEquityConversionMortgageBackedSecurityRepurchasesOutstandingValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.onitygroup.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="onit-20240930.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.onitygroup.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_8e5a8c7e-f3d7-44ee-9995-af01891ba019" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_8e5a8c7e-f3d7-44ee-9995-af01891ba019" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_8e5a8c7e-f3d7-44ee-9995-af01891ba019_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_8e5a8c7e-f3d7-44ee-9995-af01891ba019" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_8e5a8c7e-f3d7-44ee-9995-af01891ba019_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_80707f8f-b752-4159-9f34-53da52de3c02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_8e5a8c7e-f3d7-44ee-9995-af01891ba019" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_80707f8f-b752-4159-9f34-53da52de3c02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_9b70bc95-3306-4e9b-8392-d8915347b662" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_80707f8f-b752-4159-9f34-53da52de3c02" xlink:to="loc_us-gaap_SubsequentEventMember_9b70bc95-3306-4e9b-8392-d8915347b662" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_07828659-e049-4281-8248-7c8a1c2e3922" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_us-gaap_DebtInstrumentAxis_07828659-e049-4281-8248-7c8a1c2e3922" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_07828659-e049-4281-8248-7c8a1c2e3922_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_07828659-e049-4281-8248-7c8a1c2e3922" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_07828659-e049-4281-8248-7c8a1c2e3922_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_07828659-e049-4281-8248-7c8a1c2e3922" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_HMBSRelatedBorrowingsMember_f8948459-8410-470a-ab0a-e9760c786e69" xlink:href="onit-20240930.xsd#onit_HMBSRelatedBorrowingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_HMBSRelatedBorrowingsMember_f8948459-8410-470a-ab0a-e9760c786e69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PMCSeniorSecuredNotesDue2026Member_336b48f9-d8b7-429b-918b-d2eb1fbc4c4e" xlink:href="onit-20240930.xsd#onit_PMCSeniorSecuredNotesDue2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_PMCSeniorSecuredNotesDue2026Member_336b48f9-d8b7-429b-918b-d2eb1fbc4c4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_SeniorNotesDue2029Member_7c20d4d9-0c16-4adb-9c4f-035dd47ca76e" xlink:href="onit-20240930.xsd#onit_SeniorNotesDue2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_SeniorNotesDue2029Member_7c20d4d9-0c16-4adb-9c4f-035dd47ca76e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OFCSeniorSecuredNotesDue2027Member_2d40e898-1fc5-4587-a69b-cd2481b67125" xlink:href="onit-20240930.xsd#onit_OFCSeniorSecuredNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_OFCSeniorSecuredNotesDue2027Member_2d40e898-1fc5-4587-a69b-cd2481b67125" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PHHSeniorNotesMember_4d8262c0-af08-4ca5-8322-dcd28d6acc51" xlink:href="onit-20240930.xsd#onit_PHHSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_PHHSeniorNotesMember_4d8262c0-af08-4ca5-8322-dcd28d6acc51" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_WAMFinancingAgreementMember_0ca85c20-0bc6-48bc-a4b9-43a3b7738f23" xlink:href="onit-20240930.xsd#onit_WAMFinancingAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_167f6a4d-6620-4fc9-95fe-119dd16dbf85" xlink:to="loc_onit_WAMFinancingAgreementMember_0ca85c20-0bc6-48bc-a4b9-43a3b7738f23" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_bbb009cc-bb54-4c6a-a4c4-a71deda9802f" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_srt_CounterpartyNameAxis_bbb009cc-bb54-4c6a-a4c4-a71deda9802f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_bbb009cc-bb54-4c6a-a4c4-a71deda9802f_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_bbb009cc-bb54-4c6a-a4c4-a71deda9802f" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_bbb009cc-bb54-4c6a-a4c4-a71deda9802f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_bbb009cc-bb54-4c6a-a4c4-a71deda9802f" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_WaterfallMember_8ead4076-13ca-4ee5-acd5-5e70618fc3ad" xlink:href="onit-20240930.xsd#onit_WaterfallMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:to="loc_onit_WaterfallMember_8ead4076-13ca-4ee5-acd5-5e70618fc3ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewResidentialInvestmentCorpMember_9f9cc3ef-a772-4ff2-a50d-17e102658673" xlink:href="onit-20240930.xsd#onit_NewResidentialInvestmentCorpMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:to="loc_onit_NewResidentialInvestmentCorpMember_9f9cc3ef-a772-4ff2-a50d-17e102658673" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_RithmCapitalCorpAndOthersMember_16188140-72e8-47df-8e82-803d4d538af6" xlink:href="onit-20240930.xsd#onit_RithmCapitalCorpAndOthersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:to="loc_onit_RithmCapitalCorpAndOthersMember_16188140-72e8-47df-8e82-803d4d538af6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_OaktreeCapitalManagementLPAndAffiliatesMember_76b9b890-aeea-4813-8d2d-8edac60374d8" xlink:href="onit-20240930.xsd#onit_OaktreeCapitalManagementLPAndAffiliatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_18376043-4529-4089-b41e-38868b5382a8" xlink:to="loc_onit_OaktreeCapitalManagementLPAndAffiliatesMember_76b9b890-aeea-4813-8d2d-8edac60374d8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_88cd159e-d9b5-402f-8920-80df51b67315" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_88cd159e-d9b5-402f-8920-80df51b67315" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_88cd159e-d9b5-402f-8920-80df51b67315_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_88cd159e-d9b5-402f-8920-80df51b67315" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_88cd159e-d9b5-402f-8920-80df51b67315_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_c3e63699-cd21-4d66-8e67-7053ba66e6ce" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_88cd159e-d9b5-402f-8920-80df51b67315" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_c3e63699-cd21-4d66-8e67-7053ba66e6ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_NewRightsToMortgageServicingRightsAgreementsMember_bbff3cad-a9b6-4994-85d5-2556e3ca4af8" xlink:href="onit-20240930.xsd#onit_NewRightsToMortgageServicingRightsAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3e63699-cd21-4d66-8e67-7053ba66e6ce" xlink:to="loc_onit_NewRightsToMortgageServicingRightsAgreementsMember_bbff3cad-a9b6-4994-85d5-2556e3ca4af8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_MAVCanopyHoldCoILLCMember_921dfde6-c13b-44f6-88f4-1766d133930c" xlink:href="onit-20240930.xsd#onit_MAVCanopyHoldCoILLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_c3e63699-cd21-4d66-8e67-7053ba66e6ce" xlink:to="loc_onit_MAVCanopyHoldCoILLCMember_921dfde6-c13b-44f6-88f4-1766d133930c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsAxis_f0a38aa0-3827-4cd7-b723-01cee5284d8d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_us-gaap_OtherCommitmentsAxis_f0a38aa0-3827-4cd7-b723-01cee5284d8d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_f0a38aa0-3827-4cd7-b723-01cee5284d8d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherCommitmentsAxis_f0a38aa0-3827-4cd7-b723-01cee5284d8d" xlink:to="loc_us-gaap_OtherCommitmentsDomain_f0a38aa0-3827-4cd7-b723-01cee5284d8d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitmentsDomain_375a32c3-53f4-49a2-aaed-e55563682f7e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherCommitmentsAxis_f0a38aa0-3827-4cd7-b723-01cee5284d8d" xlink:to="loc_us-gaap_OtherCommitmentsDomain_375a32c3-53f4-49a2-aaed-e55563682f7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_InitialCommittedAmountMember_5b3bf4c4-094d-4477-88c7-e89db7b067a4" xlink:href="onit-20240930.xsd#onit_InitialCommittedAmountMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_375a32c3-53f4-49a2-aaed-e55563682f7e" xlink:to="loc_onit_InitialCommittedAmountMember_5b3bf4c4-094d-4477-88c7-e89db7b067a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_CommitmentAfterFirstSecuritizationOfHECMTailsMember_83a2ba8e-b2b8-40ad-a30a-b675b07ac9c7" xlink:href="onit-20240930.xsd#onit_CommitmentAfterFirstSecuritizationOfHECMTailsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherCommitmentsDomain_375a32c3-53f4-49a2-aaed-e55563682f7e" xlink:to="loc_onit_CommitmentAfterFirstSecuritizationOfHECMTailsMember_83a2ba8e-b2b8-40ad-a30a-b675b07ac9c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_44bef76d-d58a-4f82-8840-fcc9a312fcd0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_dcc6d99c-36a8-45cb-8f72-6e00ea5559a7" xlink:to="loc_us-gaap_StatementClassOfStockAxis_44bef76d-d58a-4f82-8840-fcc9a312fcd0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_44bef76d-d58a-4f82-8840-fcc9a312fcd0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_44bef76d-d58a-4f82-8840-fcc9a312fcd0" xlink:to="loc_us-gaap_ClassOfStockDomain_44bef76d-d58a-4f82-8840-fcc9a312fcd0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_140c27a6-d441-4d8e-a66e-4bc777c90560" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_44bef76d-d58a-4f82-8840-fcc9a312fcd0" xlink:to="loc_us-gaap_ClassOfStockDomain_140c27a6-d441-4d8e-a66e-4bc777c90560" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_28868614-13ef-4318-b41d-8e89accbb106" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_140c27a6-d441-4d8e-a66e-4bc777c90560" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_28868614-13ef-4318-b41d-8e89accbb106" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold_5edb92cb-af77-49ec-bc75-bc3555f0e3f9" xlink:href="onit-20240930.xsd#onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_ServicingFeeCollectedOnBehalfOfCounterpartyAmountPreviouslySold_5edb92cb-af77-49ec-bc75-bc3555f0e3f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_343cc8ef-456c-4f84-a70d-b3b304a723c0" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MortgageLoansOnRealEstateFaceAmountOfMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_srt_MortgageLoansOnRealEstateFaceAmountOfMortgages_343cc8ef-456c-4f84-a70d-b3b304a723c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_7c3b2f7d-69da-4f06-a8de-3dfeae1e569d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_7c3b2f7d-69da-4f06-a8de-3dfeae1e569d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockLiquidationPreferenceValue_91ea8ea6-6fc0-4b34-8971-fc7f251369d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockLiquidationPreferenceValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_PreferredStockLiquidationPreferenceValue_91ea8ea6-6fc0-4b34-8971-fc7f251369d5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_e09b33f0-dbf2-4cdc-b47c-f474ddbf0880" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_e09b33f0-dbf2-4cdc-b47c-f474ddbf0880" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PreferredStockDividendRatePercentageIncrease_dd194ba1-8c51-489a-9257-1601f152f4cf" xlink:href="onit-20240930.xsd#onit_PreferredStockDividendRatePercentageIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_PreferredStockDividendRatePercentageIncrease_dd194ba1-8c51-489a-9257-1601f152f4cf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PreferredStockDividendRateCapPercentage_0e3dba77-9e28-4fc7-85c8-beca1242d4da" xlink:href="onit-20240930.xsd#onit_PreferredStockDividendRateCapPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_PreferredStockDividendRateCapPercentage_0e3dba77-9e28-4fc7-85c8-beca1242d4da" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_b90ef006-8521-4b7c-a274-1bc95d051b60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_b90ef006-8521-4b7c-a274-1bc95d051b60" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_807d2058-659c-43d3-9392-52d01c0e9e19" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_807d2058-659c-43d3-9392-52d01c0e9e19" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_DebtInstrumentPaymentOfMakeWholeRedemptionPremium_01e478b2-3cec-49f8-ac6c-a3ddc111068e" xlink:href="onit-20240930.xsd#onit_DebtInstrumentPaymentOfMakeWholeRedemptionPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_DebtInstrumentPaymentOfMakeWholeRedemptionPremium_01e478b2-3cec-49f8-ac6c-a3ddc111068e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFeeAmount_090ba845-b213-4034-aa19-535c76a9a889" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFeeAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentFeeAmount_090ba845-b213-4034-aa19-535c76a9a889" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_ed6a0a8e-a48b-4231-b5dc-1b91a9545cc4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_ed6a0a8e-a48b-4231-b5dc-1b91a9545cc4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_bfb33332-07c9-46a6-aff5-9509f26d6ced" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentRepurchasedFaceAmount_bfb33332-07c9-46a6-aff5-9509f26d6ced" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_6a45712b-09b5-4b85-8d33-ef6011be166b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_6a45712b-09b5-4b85-8d33-ef6011be166b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_59b8c562-aaa8-4f44-a345-5a34345489c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_59b8c562-aaa8-4f44-a345-5a34345489c2" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_581eb2f4-27f8-4f07-b254-88c1fa16caf3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_581eb2f4-27f8-4f07-b254-88c1fa16caf3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_bdafd1fb-550a-4ca7-a76c-2fd369cd8285" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_bdafd1fb-550a-4ca7-a76c-2fd369cd8285" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_d6916b3f-eda3-494f-83c8-cc3d93defa83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_d6916b3f-eda3-494f-83c8-cc3d93defa83" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_265347a2-ab0a-4dcb-83ab-42ed2581e977" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_LongTermDebt_265347a2-ab0a-4dcb-83ab-42ed2581e977" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightOutstanding_97034fbb-9e94-41f3-8bc2-10e40b729520" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_ClassOfWarrantOrRightOutstanding_97034fbb-9e94-41f3-8bc2-10e40b729520" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_7412d5ee-4ec9-4e66-93ac-860eee9caf49" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_7412d5ee-4ec9-4e66-93ac-860eee9caf49" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualObligation_a6683407-6ce7-44dd-afe5-ed7c8473ae52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractualObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_ContractualObligation_a6683407-6ce7-44dd-afe5-ed7c8473ae52" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCash_0bab9180-b6de-4b26-bcc9-af98ea5146fe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_us-gaap_RestrictedCash_0bab9180-b6de-4b26-bcc9-af98ea5146fe" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetAcquisitionBookValue_fbe004b4-4461-401a-928e-0240fd625d9f" xlink:href="onit-20240930.xsd#onit_AssetAcquisitionBookValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_AssetAcquisitionBookValue_fbe004b4-4461-401a-928e-0240fd625d9f" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_AssetAcquisitionCash_6b5543d1-e2f5-4414-a016-10fdc621db28" xlink:href="onit-20240930.xsd#onit_AssetAcquisitionCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_AssetAcquisitionCash_6b5543d1-e2f5-4414-a016-10fdc621db28" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PreferredStockDividendAccrualRateTerm_37c5a925-1f7e-4f7b-9617-d129c4fdc35d" xlink:href="onit-20240930.xsd#onit_PreferredStockDividendAccrualRateTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_PreferredStockDividendAccrualRateTerm_37c5a925-1f7e-4f7b-9617-d129c4fdc35d" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PreferredStockRepurchasePricePercentageOfPrincipal_a2d7d0ac-fdef-4e80-bed3-cb7ae02acbf8" xlink:href="onit-20240930.xsd#onit_PreferredStockRepurchasePricePercentageOfPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_PreferredStockRepurchasePricePercentageOfPrincipal_a2d7d0ac-fdef-4e80-bed3-cb7ae02acbf8" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_PreferredStockResaleRegistrationAgreementMaximumTerm_d8c9f608-52b4-4019-9704-72177458d70f" xlink:href="onit-20240930.xsd#onit_PreferredStockResaleRegistrationAgreementMaximumTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_PreferredStockResaleRegistrationAgreementMaximumTerm_d8c9f608-52b4-4019-9704-72177458d70f" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_onit_LoanAndSecurityAgreementRevolvingBasisTerm_a7972697-563e-45d6-8e9b-2659e4af3b89" xlink:href="onit-20240930.xsd#onit_LoanAndSecurityAgreementRevolvingBasisTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cb2309a-27e2-4c4b-8cf4-0e2118181355" xlink:to="loc_onit_LoanAndSecurityAgreementRevolvingBasisTerm_a7972697-563e-45d6-8e9b-2659e4af3b89" xlink:type="arc" order="28"/>
  </link:definitionLink>
</link:linkbase>
