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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019caf3a-ca36-7756-92ac-667fad73ad0d,g:2021b17c-b52e-4c0c-974a-bfcf9a5457ee-->
<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.qnityelectronics.com/role/ConsolidatedStatementsofChangesinEquityUnaudited" xlink:type="simple" xlink:href="q-20260331.xsd#ConsolidatedStatementsofChangesinEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/ConsolidatedStatementsofChangesinEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019caf3a-cc4c-764d-854f-0b0e93a019f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019caf3a-cc4c-72ad-87f9-e78ddb993bd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019caf3a-cc4c-764d-854f-0b0e93a019f0" xlink:to="loc_us-gaap_StatementTable_019caf3a-cc4c-72ad-87f9-e78ddb993bd1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cc4c-7424-8328-213e1ed5099e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019caf3a-cc4c-72ad-87f9-e78ddb993bd1" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cc4c-7424-8328-213e1ed5099e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7424-8328-213e1ed5099e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cc4c-7424-8328-213e1ed5099e" xlink:to="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7424-8328-213e1ed5099e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cc4c-7424-8328-213e1ed5099e" xlink:to="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019d3dfc-e4b3-7fd6-a923-5f1b13661d68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_CommonStockMember_019d3dfc-e4b3-7fd6-a923-5f1b13661d68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019d3df5-7e62-7f6a-82af-c8f4d00e35ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_PreferredStockMember_019d3df5-7e62-7f6a-82af-c8f4d00e35ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019d3df4-a3f6-74d5-8595-d6de93acae51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019d3df4-a3f6-74d5-8595-d6de93acae51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019d3df4-1a97-7916-b9ed-6ccf0f598c09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_RetainedEarningsMember_019d3df4-1a97-7916-b9ed-6ccf0f598c09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ParentCompanyNetInvestmentMember_019caf3a-cc4c-7258-9b7d-b5bf7e2639c7" xlink:href="q-20260331.xsd#q_ParentCompanyNetInvestmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_q_ParentCompanyNetInvestmentMember_019caf3a-cc4c-7258-9b7d-b5bf7e2639c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cc4c-76a7-8fa4-6c0c4627de69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cc4c-76a7-8fa4-6c0c4627de69" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019caf3a-cc4c-7648-97b7-5c02181e227b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cc4c-7e54-8e0a-42801fa040bb" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019caf3a-cc4c-7648-97b7-5c02181e227b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019caf3a-cc4c-764d-854f-0b0e93a019f0" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cc4c-72d9-847f-92513f45024e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cc4c-72d9-847f-92513f45024e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019caf3a-cc4c-7014-b242-4f3d4b154ee2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_ProfitLoss_019caf3a-cc4c-7014-b242-4f3d4b154ee2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019caf3a-cc4c-708c-bb55-5bb6554a68d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019caf3a-cc4c-708c-bb55-5bb6554a68d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019caf3a-cc4c-7e6d-8f90-a064ba78d0b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019caf3a-cc4c-7e6d-8f90-a064ba78d0b8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransferToParentCompany_019caf3a-cc4c-7b01-85b5-252d70fee114" xlink:href="q-20260331.xsd#q_TransferToParentCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_q_TransferToParentCompany_019caf3a-cc4c-7b01-85b5-252d70fee114" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019d3df4-a3f6-72f6-a8af-0f7df9d2861a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019d3df4-a3f6-72f6-a8af-0f7df9d2861a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019d3e01-c993-7756-b37a-1c5fa19d57c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019d3e01-c993-7756-b37a-1c5fa19d57c9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments_019db818-5e25-7ad4-9bb7-c1c1286b835a" xlink:href="q-20260331.xsd#q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments_019db818-5e25-7ad4-9bb7-c1c1286b835a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019db816-027f-71a3-b9a7-0b52abb749c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019caf3a-cc4c-705a-bb15-7b1b5b6548df" xlink:to="loc_us-gaap_StockholdersEquityOther_019db816-027f-71a3-b9a7-0b52abb749c5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cc4c-7ce5-a841-6af4f51e59a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/REVENUENarrativeDetails" xlink:type="simple" xlink:href="q-20260331.xsd#REVENUENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/REVENUENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7672-9e22-cbdc1867fa4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-768c-a2da-5b7afdf1f5bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7672-9e22-cbdc1867fa4a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-768c-a2da-5b7afdf1f5bf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-7149-bb82-d5331a2dad6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-768c-a2da-5b7afdf1f5bf" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-7149-bb82-d5331a2dad6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-7149-bb82-d5331a2dad6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-7149-bb82-d5331a2dad6a" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-7149-bb82-d5331a2dad6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-7b98-b6ea-c74bacf87781" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-7149-bb82-d5331a2dad6a" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-7b98-b6ea-c74bacf87781" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_019caf3a-cc4c-7b78-8e6a-ad3d58c09dd3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-7b98-b6ea-c74bacf87781" xlink:to="loc_us-gaap_SalesRevenueNetMember_019caf3a-cc4c-7b78-8e6a-ad3d58c09dd3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7d95-aa07-78517c33bec2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-768c-a2da-5b7afdf1f5bf" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7d95-aa07-78517c33bec2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7d95-aa07-78517c33bec2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7d95-aa07-78517c33bec2" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7d95-aa07-78517c33bec2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7386-9309-7bb33df50eae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7d95-aa07-78517c33bec2" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7386-9309-7bb33df50eae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019caf3a-cc4c-7a01-92f8-77cc39941d0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7386-9309-7bb33df50eae" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019caf3a-cc4c-7a01-92f8-77cc39941d0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019caf3a-cc4c-778f-a3c0-0ee3276c88ff" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-768c-a2da-5b7afdf1f5bf" xlink:to="loc_srt_MajorCustomersAxis_019caf3a-cc4c-778f-a3c0-0ee3276c88ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-778f-a3c0-0ee3276c88ff_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019caf3a-cc4c-778f-a3c0-0ee3276c88ff" xlink:to="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-778f-a3c0-0ee3276c88ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-79c9-b7e0-8fccb85bafcf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019caf3a-cc4c-778f-a3c0-0ee3276c88ff" xlink:to="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-79c9-b7e0-8fccb85bafcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SamsungElectronicsCompanyLimitedMember_019caf3a-cc4c-73c0-bacc-5e98b012e0bc" xlink:href="q-20260331.xsd#q_SamsungElectronicsCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-79c9-b7e0-8fccb85bafcf" xlink:to="loc_q_SamsungElectronicsCompanyLimitedMember_019caf3a-cc4c-73c0-bacc-5e98b012e0bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TaiwanSemiconductorManufacturingCompanyLimitedMember_019caf3a-cc4c-78f2-9b49-408461eb159f" xlink:href="q-20260331.xsd#q_TaiwanSemiconductorManufacturingCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019caf3a-cc4c-79c9-b7e0-8fccb85bafcf" xlink:to="loc_q_TaiwanSemiconductorManufacturingCompanyLimitedMember_019caf3a-cc4c-78f2-9b49-408461eb159f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019caf3a-cc4c-7dcd-be5d-8d4d15069f45" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7672-9e22-cbdc1867fa4a" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019caf3a-cc4c-7dcd-be5d-8d4d15069f45" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/REVENUEScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="q-20260331.xsd#REVENUEScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/REVENUEScheduleofDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7a01-8217-db48b1e6594c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-7a29-ae47-6056590d189c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7a01-8217-db48b1e6594c" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-7a29-ae47-6056590d189c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7be5-bf03-5b3eff73cd58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-7a29-ae47-6056590d189c" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7be5-bf03-5b3eff73cd58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7be5-bf03-5b3eff73cd58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7be5-bf03-5b3eff73cd58" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7be5-bf03-5b3eff73cd58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7452-8018-c043984a622b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7be5-bf03-5b3eff73cd58" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7452-8018-c043984a622b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019caf3a-cc4c-7020-b7ae-0c2acc105269" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7452-8018-c043984a622b" xlink:to="loc_q_SemiconductorTechnologiesMember_019caf3a-cc4c-7020-b7ae-0c2acc105269" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsMember_019caf3a-cc4c-7262-a40c-1e1520e8cca5" xlink:href="q-20260331.xsd#q_InterconnectSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7452-8018-c043984a622b" xlink:to="loc_q_InterconnectSolutionsMember_019caf3a-cc4c-7262-a40c-1e1520e8cca5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019caf3a-cc4c-7104-922d-0d913879f1dd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019caf3a-cc4c-7a29-ae47-6056590d189c" xlink:to="loc_srt_StatementGeographicalAxis_019caf3a-cc4c-7104-922d-0d913879f1dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7104-922d-0d913879f1dd_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019caf3a-cc4c-7104-922d-0d913879f1dd" xlink:to="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7104-922d-0d913879f1dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019caf3a-cc4c-7104-922d-0d913879f1dd" xlink:to="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_019caf3a-cc4c-76d9-889b-b598e81af87a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:to="loc_srt_AmericasMember_019caf3a-cc4c-76d9-889b-b598e81af87a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019caf3a-cc4c-7541-b34f-6b551c5dafd6" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:to="loc_country_US_019caf3a-cc4c-7541-b34f-6b551c5dafd6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_AmericasExcludingTheUnitedStatesMember_019caf3a-cc4c-7789-92e0-b8c4a5c068c7" xlink:href="q-20260331.xsd#q_AmericasExcludingTheUnitedStatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:to="loc_q_AmericasExcludingTheUnitedStatesMember_019caf3a-cc4c-7789-92e0-b8c4a5c068c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_019caf3a-cc4c-7757-abd0-64bfa464b7bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:to="loc_us-gaap_EMEAMember_019caf3a-cc4c-7757-abd0-64bfa464b7bc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_019caf3a-cc4c-791a-8bc2-6ae74f3e6aa1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019caf3a-cc4c-7476-a255-d9976f44754b" xlink:to="loc_srt_AsiaPacificMember_019caf3a-cc4c-791a-8bc2-6ae74f3e6aa1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_019caf3a-cc4c-7e3b-995d-871745c7b12d" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AsiaPacificMember_019caf3a-cc4c-791a-8bc2-6ae74f3e6aa1" xlink:to="loc_country_CN_019caf3a-cc4c-7e3b-995d-871745c7b12d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019caf3a-cc4c-7b7c-82d4-d691d6eeff12" xlink:href="q-20260331.xsd#q_SouthKoreaTaiwanAndOtherAsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AsiaPacificMember_019caf3a-cc4c-791a-8bc2-6ae74f3e6aa1" xlink:to="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019caf3a-cc4c-7b7c-82d4-d691d6eeff12" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_KR_019caf3a-cc4c-7efd-b737-73707a875752" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_KR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019caf3a-cc4c-7b7c-82d4-d691d6eeff12" xlink:to="loc_country_KR_019caf3a-cc4c-7efd-b737-73707a875752" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_TW_019caf3a-cc4c-7e5a-af37-eed8ee963266" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_TW"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019caf3a-cc4c-7b7c-82d4-d691d6eeff12" xlink:to="loc_country_TW_019caf3a-cc4c-7e5a-af37-eed8ee963266" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OtherMember_019caf3a-cc4c-75f2-ad40-361692cc6fef" xlink:href="q-20260331.xsd#q_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019caf3a-cc4c-7b7c-82d4-d691d6eeff12" xlink:to="loc_q_OtherMember_019caf3a-cc4c-75f2-ad40-361692cc6fef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf3a-cc4c-74af-844f-289e39f7b973" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019caf3a-cc4c-7a01-8217-db48b1e6594c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019caf3a-cc4c-74af-844f-289e39f7b973" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails" xlink:type="simple" xlink:href="q-20260331.xsd#RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-730c-a790-20730879e321" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-730c-a790-20730879e321" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7209-8c52-ed22594c726c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-730c-a790-20730879e321" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7209-8c52-ed22594c726c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7209-8c52-ed22594c726c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7209-8c52-ed22594c726c" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7209-8c52-ed22594c726c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-77d9-9d92-31199fee6d21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7209-8c52-ed22594c726c" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-77d9-9d92-31199fee6d21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-738a-bfca-890f54585556" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-77d9-9d92-31199fee6d21" xlink:to="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-738a-bfca-890f54585556" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019caf3a-cc4c-786d-b7c6-751d4821ac9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019caf3a-cc4c-786d-b7c6-751d4821ac9b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019caf3a-cc4c-7ba2-8908-7aff09061602" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019caf3a-cc4c-7ba2-8908-7aff09061602" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019caf3a-cc4c-7f32-ba42-3bfea13ae473" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019caf3a-cc4c-7f32-ba42-3bfea13ae473" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationIntegrationAndOtherCharges_019caf3a-cc4c-7eda-a1a8-424ca60a432e" xlink:href="q-20260331.xsd#q_TransformationIntegrationAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_q_TransformationIntegrationAndOtherCharges_019caf3a-cc4c-7eda-a1a8-424ca60a432e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019caf3a-cc4c-70f8-916f-ac06783fdf0f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7447-9138-9cb8ca2b5671" xlink:to="loc_us-gaap_OperatingExpenses_019caf3a-cc4c-70f8-916f-ac06783fdf0f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails" xlink:type="simple" xlink:href="q-20260331.xsd#RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-7641-a644-ad09ba224de5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-7641-a644-ad09ba224de5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7068-a997-fe8d8a560ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019caf3a-cc4c-7641-a644-ad09ba224de5" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7068-a997-fe8d8a560ce2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7068-a997-fe8d8a560ce2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7068-a997-fe8d8a560ce2" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7068-a997-fe8d8a560ce2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7e90-bb44-57b8ec464697" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-7068-a997-fe8d8a560ce2" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7e90-bb44-57b8ec464697" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-7797-bcee-3beeddbdab6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7e90-bb44-57b8ec464697" xlink:to="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-7797-bcee-3beeddbdab6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_CashPoolingAndGeneralFinancingActivities_019caf3a-cc4c-7f2e-a02b-0ead13922d4a" xlink:href="q-20260331.xsd#q_CashPoolingAndGeneralFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_CashPoolingAndGeneralFinancingActivities_019caf3a-cc4c-7f2e-a02b-0ead13922d4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_CorporateCostAllocations_019caf3a-cc4c-7d62-99c5-dfbcdde6b341" xlink:href="q-20260331.xsd#q_CorporateCostAllocations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_CorporateCostAllocations_019caf3a-cc4c-7d62-99c5-dfbcdde6b341" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TaxesDeemedSettledWithParent_019caf3a-cc4c-76d4-aed9-ae70bf8bb5f1" xlink:href="q-20260331.xsd#q_TaxesDeemedSettledWithParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_TaxesDeemedSettledWithParent_019caf3a-cc4c-76d4-aed9-ae70bf8bb5f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_PaymentToTransfersToParentNet_019caf3a-cc4c-75f9-b14e-2434dd9b457e" xlink:href="q-20260331.xsd#q_PaymentToTransfersToParentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_PaymentToTransfersToParentNet_019caf3a-cc4c-75f9-b14e-2434dd9b457e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_StockBasedCompensationAndOtherNoncashTransfersToParent_019caf3a-cc4c-768c-8e7f-4851773b3881" xlink:href="q-20260331.xsd#q_StockBasedCompensationAndOtherNoncashTransfersToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_StockBasedCompensationAndOtherNoncashTransfersToParent_019caf3a-cc4c-768c-8e7f-4851773b3881" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ParentCompanyEquityTransfersToParentNet_019caf3a-cc4c-7ac8-ad6a-cc31fc757be9" xlink:href="q-20260331.xsd#q_ParentCompanyEquityTransfersToParentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019caf3a-cc4c-7348-92bc-0d2f02e3554c" xlink:to="loc_q_ParentCompanyEquityTransfersToParentNet_019caf3a-cc4c-7ac8-ad6a-cc31fc757be9" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/NONCONSOLIDATEDAFFILIATESDetails" xlink:type="simple" xlink:href="q-20260331.xsd#NONCONSOLIDATEDAFFILIATESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/NONCONSOLIDATEDAFFILIATESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:to="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019caf3a-cc4c-7f8e-a81d-98883ed65643" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019caf3a-cc4c-7f8e-a81d-98883ed65643" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019caf3a-cc4c-7f8e-a81d-98883ed65643_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019caf3a-cc4c-7f8e-a81d-98883ed65643" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019caf3a-cc4c-7f8e-a81d-98883ed65643_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019caf3a-cc4c-70c9-bbbd-e8d9f3406219" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019caf3a-cc4c-7f8e-a81d-98883ed65643" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019caf3a-cc4c-70c9-bbbd-e8d9f3406219" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_HitachiChemDuPMicrosystemsLLCMember_019caf3a-cc4c-7d3d-8d92-a298a724303a" xlink:href="q-20260331.xsd#q_HitachiChemDuPMicrosystemsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019caf3a-cc4c-70c9-bbbd-e8d9f3406219" xlink:to="loc_q_HitachiChemDuPMicrosystemsLLCMember_019caf3a-cc4c-7d3d-8d92-a298a724303a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-77c3-ad50-ccce0118aadf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-77c3-ad50-ccce0118aadf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-77c3-ad50-ccce0118aadf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-77c3-ad50-ccce0118aadf" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-77c3-ad50-ccce0118aadf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7094-8f71-d16e47c3844c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019caf3a-cc4c-77c3-ad50-ccce0118aadf" xlink:to="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7094-8f71-d16e47c3844c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-7243-a72c-1df0ecb84203" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7094-8f71-d16e47c3844c" xlink:to="loc_us-gaap_RelatedPartyMember_019caf3a-cc4c-7243-a72c-1df0ecb84203" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_019caf3a-cc4c-7dd1-bbd5-233837ab33a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019caf3a-cc4c-7094-8f71-d16e47c3844c" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_019caf3a-cc4c-7dd1-bbd5-233837ab33a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-748c-94aa-f0b83a69b1fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-748c-94aa-f0b83a69b1fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-748c-94aa-f0b83a69b1fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-748c-94aa-f0b83a69b1fc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-748c-94aa-f0b83a69b1fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-768d-8b44-260ab2d6704f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019caf3a-cc4c-748c-94aa-f0b83a69b1fc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-768d-8b44-260ab2d6704f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_019caf3a-cc4c-7a44-aa34-84c8c224ebd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-768d-8b44-260ab2d6704f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_019caf3a-cc4c-7a44-aa34-84c8c224ebd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsTotalMember_019caf3a-cc4c-7441-b4ec-1771de26350f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019caf3a-cc4c-768d-8b44-260ab2d6704f" xlink:to="loc_us-gaap_CostOfGoodsTotalMember_019caf3a-cc4c-7441-b4ec-1771de26350f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7654-8774-47654e1d0cdc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019caf3a-cc4c-7ee6-9123-98d0723357ff" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7654-8774-47654e1d0cdc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7654-8774-47654e1d0cdc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7654-8774-47654e1d0cdc" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7654-8774-47654e1d0cdc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7a60-be9c-37244c18d3ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019caf3a-cc4c-7654-8774-47654e1d0cdc" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7a60-be9c-37244c18d3ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019caf3a-cc4c-7be2-9f5b-6097f51c8280" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7a60-be9c-37244c18d3ef" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019caf3a-cc4c-7be2-9f5b-6097f51c8280" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplierConcentrationRiskMember_019caf3a-cc4c-71f0-be83-b492c4369c5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SupplierConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019caf3a-cc4c-7a60-be9c-37244c18d3ef" xlink:to="loc_us-gaap_SupplierConcentrationRiskMember_019caf3a-cc4c-71f0-be83-b492c4369c5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EquityMethodInvestmentNetOfInvestmentLiabilities_019caf3a-cc4c-70b7-b1b1-5ead325a5bbc" xlink:href="q-20260331.xsd#q_EquityMethodInvestmentNetOfInvestmentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:to="loc_q_EquityMethodInvestmentNetOfInvestmentLiabilities_019caf3a-cc4c-70b7-b1b1-5ead325a5bbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayable_019caf3a-cc4c-725b-9584-8b81c55edc98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:to="loc_us-gaap_NotesPayable_019caf3a-cc4c-725b-9584-8b81c55edc98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019caf3a-cc4c-7776-8a16-3d92dc678277" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019caf3a-cc4c-7776-8a16-3d92dc678277" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates_019caf3a-cc4c-7569-a3f1-fe501c55271f" xlink:href="q-20260331.xsd#q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesLineItems_019caf3a-cc4c-77f7-8d09-d0b3847e6dd6" xlink:to="loc_q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates_019caf3a-cc4c-7569-a3f1-fe501c55271f" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails" xlink:type="simple" xlink:href="q-20260331.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_019caf3a-cc4c-7a71-ae53-4e7c651496d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_019caf3a-cc4c-7ec6-bfcc-d864a8d5c258" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_019caf3a-cc4c-7a71-ae53-4e7c651496d1" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_019caf3a-cc4c-7ec6-bfcc-d864a8d5c258" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019caf3a-cc4c-7ec6-bfcc-d864a8d5c258" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7924-af4f-d1741c500cc9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cc4c-7edf-a33d-fa6b9abf9f8e" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7924-af4f-d1741c500cc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019caf3a-cc4c-7afe-89a8-17ec1650feac" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7924-af4f-d1741c500cc9" xlink:to="loc_q_SemiconductorTechnologiesMember_019caf3a-cc4c-7afe-89a8-17ec1650feac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsMember_019caf3a-cc4c-7b30-9757-9e4bf02058d8" xlink:href="q-20260331.xsd#q_InterconnectSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cc4c-7924-af4f-d1741c500cc9" xlink:to="loc_q_InterconnectSolutionsMember_019caf3a-cc4c-7b30-9757-9e4bf02058d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_019caf3a-cc4c-7281-b4b5-a52fbddc1b68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019caf3a-cc4c-7a71-ae53-4e7c651496d1" xlink:to="loc_us-gaap_GoodwillRollForward_019caf3a-cc4c-7281-b4b5-a52fbddc1b68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019caf3a-cc4c-722e-b83e-c11f54b0d2a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019caf3a-cc4c-7281-b4b5-a52fbddc1b68" xlink:to="loc_us-gaap_Goodwill_019caf3a-cc4c-722e-b83e-c11f54b0d2a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_019caf3a-cc4c-7f51-b45c-876eaa85c7c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019caf3a-cc4c-7281-b4b5-a52fbddc1b68" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_019caf3a-cc4c-7f51-b45c-876eaa85c7c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019caf3a-cc4c-7b8e-811c-a254d5afbbf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails" xlink:type="simple" xlink:href="q-20260331.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019caf3a-cd04-778b-8afe-75b8589a057e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019caf3a-cc4c-7bb7-8eaa-616b0f3b6c01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019caf3a-cd04-778b-8afe-75b8589a057e" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019caf3a-cc4c-7bb7-8eaa-616b0f3b6c01" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019caf3a-cc4c-72ca-9466-bbfffd4d258a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019caf3a-cc4c-7bb7-8eaa-616b0f3b6c01" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019caf3a-cc4c-72ca-9466-bbfffd4d258a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-72ca-9466-bbfffd4d258a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019caf3a-cc4c-72ca-9466-bbfffd4d258a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-72ca-9466-bbfffd4d258a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-7149-a5aa-f8b3af314d4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019caf3a-cc4c-72ca-9466-bbfffd4d258a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-7149-a5aa-f8b3af314d4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_019caf3a-cc4c-7ad1-b06e-b15bae46e42b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-7149-a5aa-f8b3af314d4c" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_019caf3a-cc4c-7ad1-b06e-b15bae46e42b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_019caf3a-cc4c-7ff7-8ea2-1bc212d7ca52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-7149-a5aa-f8b3af314d4c" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_019caf3a-cc4c-7ff7-8ea2-1bc212d7ca52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019caf3a-cc4c-74af-b4b2-c80e892918fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019caf3a-cc4c-7149-a5aa-f8b3af314d4c" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019caf3a-cc4c-74af-b4b2-c80e892918fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019caf3a-cd04-7d79-b41b-1b9bf01b58dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019caf3a-cd04-778b-8afe-75b8589a057e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019caf3a-cd04-7d79-b41b-1b9bf01b58dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019caf3a-cd04-7525-8109-68de0cc730d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019caf3a-cd04-778b-8afe-75b8589a057e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019caf3a-cd04-7525-8109-68de0cc730d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019caf3a-cd04-7e90-98bb-940803f3ad7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019caf3a-cd04-778b-8afe-75b8589a057e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019caf3a-cd04-7e90-98bb-940803f3ad7e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails" xlink:type="simple" xlink:href="q-20260331.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_q_ScheduleofIntangibleAssetsLineItems_019caf3a-cd04-7e27-8471-1a27a3475cac" xlink:href="q-20260331.xsd#q_ScheduleofIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ScheduleofIntangibleAssetsTable_019caf3a-cd04-7ede-88b9-729b113a3380" xlink:href="q-20260331.xsd#q_ScheduleofIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_q_ScheduleofIntangibleAssetsLineItems_019caf3a-cd04-7e27-8471-1a27a3475cac" xlink:to="loc_q_ScheduleofIntangibleAssetsTable_019caf3a-cd04-7ede-88b9-729b113a3380" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7492-ab59-e0b6e85d2931" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_q_ScheduleofIntangibleAssetsTable_019caf3a-cd04-7ede-88b9-729b113a3380" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7492-ab59-e0b6e85d2931" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7492-ab59-e0b6e85d2931_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7492-ab59-e0b6e85d2931" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7492-ab59-e0b6e85d2931_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7985-bc87-25ff077e04b7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7492-ab59-e0b6e85d2931" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7985-bc87-25ff077e04b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7e90-9f8a-5db6b1d02d6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7985-bc87-25ff077e04b7" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7e90-9f8a-5db6b1d02d6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7c03-809c-c3f7ff42fc02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_q_ScheduleofIntangibleAssetsTable_019caf3a-cd04-7ede-88b9-729b113a3380" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7c03-809c-c3f7ff42fc02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c03-809c-c3f7ff42fc02_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7c03-809c-c3f7ff42fc02" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c03-809c-c3f7ff42fc02_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-71c0-908f-e94e0840288f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7c03-809c-c3f7ff42fc02" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-71c0-908f-e94e0840288f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019caf3a-cd04-7db4-8c97-5977c4a697ec" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-71c0-908f-e94e0840288f" xlink:to="loc_q_SemiconductorTechnologiesMember_019caf3a-cd04-7db4-8c97-5977c4a697ec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndustrialsCoSegmentMember_019caf3a-cd04-78a9-bc97-f68988c77868" xlink:href="q-20260331.xsd#q_IndustrialsCoSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-71c0-908f-e94e0840288f" xlink:to="loc_q_IndustrialsCoSegmentMember_019caf3a-cd04-78a9-bc97-f68988c77868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019caf3a-cd04-7c0a-a6a8-3664412f6569" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_ScheduleofIntangibleAssetsLineItems_019caf3a-cd04-7e27-8471-1a27a3475cac" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019caf3a-cd04-7c0a-a6a8-3664412f6569" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails" xlink:type="simple" xlink:href="q-20260331.xsd#SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019db83d-f080-781c-8352-7a1e1cb54dc5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:to="loc_us-gaap_DebtInstrumentAxis_019db83d-f080-781c-8352-7a1e1cb54dc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-781c-8352-7a1e1cb54dc5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019db83d-f080-781c-8352-7a1e1cb54dc5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-781c-8352-7a1e1cb54dc5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-7527-b52a-cb1eeea45af3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019db83d-f080-781c-8352-7a1e1cb54dc5" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-7527-b52a-cb1eeea45af3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member_019db83d-f080-787e-b268-97b301243c76" xlink:href="q-20260331.xsd#q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-7527-b52a-cb1eeea45af3" xlink:to="loc_q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member_019db83d-f080-787e-b268-97b301243c76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SeniorSecuredCreditFacilitiesMember_019db83d-f080-76b4-a1b8-95f9b118f8a1" xlink:href="q-20260331.xsd#q_SeniorSecuredCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019db83d-f080-7527-b52a-cb1eeea45af3" xlink:to="loc_q_SeniorSecuredCreditFacilitiesMember_019db83d-f080-76b4-a1b8-95f9b118f8a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019db83d-f080-7f2d-88f7-914ebb6c8e43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019db83d-f080-7f2d-88f7-914ebb6c8e43" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019db83d-f080-7f2d-88f7-914ebb6c8e43_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019db83d-f080-7f2d-88f7-914ebb6c8e43" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019db83d-f080-7f2d-88f7-914ebb6c8e43_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019db83d-f080-78bc-8635-249015426dcd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019db83d-f080-7f2d-88f7-914ebb6c8e43" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019db83d-f080-78bc-8635-249015426dcd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019db83d-f080-76e3-a062-f92797113aa5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019db83d-f080-78bc-8635-249015426dcd" xlink:to="loc_us-gaap_LineOfCreditMember_019db83d-f080-76e3-a062-f92797113aa5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e09a7-0c11-72c5-95f4-a8fc9bb01b57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:to="loc_us-gaap_CreditFacilityAxis_019e09a7-0c11-72c5-95f4-a8fc9bb01b57" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72c5-95f4-a8fc9bb01b57_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e09a7-0c11-72c5-95f4-a8fc9bb01b57" xlink:to="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72c5-95f4-a8fc9bb01b57_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72b6-88d9-f3531e51afdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e09a7-0c11-72c5-95f4-a8fc9bb01b57" xlink:to="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72b6-88d9-f3531e51afdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e09a7-0c11-7ae1-ba63-90ca6d7f3848" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72b6-88d9-f3531e51afdb" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e09a7-0c11-7ae1-ba63-90ca6d7f3848" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_019e09a7-a946-7796-be1b-758c1692e2d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e09a7-0c11-72b6-88d9-f3531e51afdb" xlink:to="loc_us-gaap_LetterOfCreditMember_019e09a7-a946-7796-be1b-758c1692e2d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e09d6-bb13-74c6-930c-34ec21966ab4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019db83d-f080-78d6-80f4-9bb5cd8d09e8" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e09d6-bb13-74c6-930c-34ec21966ab4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e09d6-bb13-74c6-930c-34ec21966ab4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e09d6-bb13-74c6-930c-34ec21966ab4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e09d6-bb13-74c6-930c-34ec21966ab4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e09d6-bb13-7367-967e-e2034e4e7dc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e09d6-bb13-74c6-930c-34ec21966ab4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e09d6-bb13-7367-967e-e2034e4e7dc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e09d6-bb13-72fe-8033-c772a2fe355f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e09d6-bb13-7367-967e-e2034e4e7dc4" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e09d6-bb13-72fe-8033-c772a2fe355f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_019d9190-16e3-7c62-905b-85879fb3c075" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_DebtCurrent_019d9190-16e3-7c62-905b-85879fb3c075" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019d3e8f-fc50-7bc7-acf0-baae7ca3e74a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019d3e8f-fc50-7bc7-acf0-baae7ca3e74a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019e09d6-bb13-7bdc-853a-5b4566185e95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_LongTermDebtFairValue_019e09d6-bb13-7bdc-853a-5b4566185e95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019d3e8f-fc50-77b9-9b79-98f7c9f57fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019d3e8f-fc50-77b9-9b79-98f7c9f57fb2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount_019d3e8f-fc50-7256-9301-63a80d34ab14" xlink:href="q-20260331.xsd#q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount_019d3e8f-fc50-7256-9301-63a80d34ab14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e09a7-0c11-7259-9f13-8b81c285884d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e09a7-0c11-7259-9f13-8b81c285884d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_019e0d9d-0adb-7d00-aa20-1c4299f8c31e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019db83d-f080-74fb-8fab-afe5b0d79a2c" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_019e0d9d-0adb-7d00-aa20-1c4299f8c31e" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails" xlink:type="simple" xlink:href="q-20260331.xsd#COMMITMENTSANDCONTINGENTLIABILITIESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-70b5-8f83-2a0263ae3186" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_019d3e9c-64a9-7fb7-8b91-ca5f73153ff7" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-70b5-8f83-2a0263ae3186" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_AccruedAndOtherCurrentLiabilitiesMember_019d3e9c-64a9-7795-8979-3b9143c81aa6" xlink:href="q-20260331.xsd#q_AccruedAndOtherCurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-70b5-8f83-2a0263ae3186" xlink:to="loc_q_AccruedAndOtherCurrentLiabilitiesMember_019d3e9c-64a9-7795-8979-3b9143c81aa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OtherNoncurrentObligationsMember_019d3e9c-64a9-79e1-891b-d218b33323f8" xlink:href="q-20260331.xsd#q_OtherNoncurrentObligationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_019d3e9c-64a9-70b5-8f83-2a0263ae3186" xlink:to="loc_q_OtherNoncurrentObligationsMember_019d3e9c-64a9-79e1-891b-d218b33323f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019d3e9c-64a9-7f22-beef-23050753f088" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:to="loc_dei_LegalEntityAxis_019d3e9c-64a9-7f22-beef-23050753f088" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019d3e9c-64a9-7f22-beef-23050753f088_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019d3e9c-64a9-7f22-beef-23050753f088" xlink:to="loc_dei_EntityDomain_019d3e9c-64a9-7f22-beef-23050753f088_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019d3e9c-64a9-763e-b14c-3a19e9f40331" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019d3e9c-64a9-7f22-beef-23050753f088" xlink:to="loc_dei_EntityDomain_019d3e9c-64a9-763e-b14c-3a19e9f40331" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DuPontMember_019d3e9c-64a9-7b9e-abdb-b04fff8fef7d" xlink:href="q-20260331.xsd#q_DuPontMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019d3e9c-64a9-763e-b14c-3a19e9f40331" xlink:to="loc_q_DuPontMember_019d3e9c-64a9-7b9e-abdb-b04fff8fef7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019d3e9c-64a9-7c90-ae93-e700a96a49cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019d3e9c-64a9-7c90-ae93-e700a96a49cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019d3e9c-64a9-7c90-ae93-e700a96a49cc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019d3e9c-64a9-7c90-ae93-e700a96a49cc" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019d3e9c-64a9-7c90-ae93-e700a96a49cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019d3e9c-64a9-7583-95dd-aa8b4131eb91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019d3e9c-64a9-7c90-ae93-e700a96a49cc" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019d3e9c-64a9-7583-95dd-aa8b4131eb91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ApplicableQnityPercentageMember_019d3e9c-64a9-7c2e-a1f6-f4f29ac28dd7" xlink:href="q-20260331.xsd#q_ApplicableQnityPercentageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019d3e9c-64a9-7583-95dd-aa8b4131eb91" xlink:to="loc_q_ApplicableQnityPercentageMember_019d3e9c-64a9-7c2e-a1f6-f4f29ac28dd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019d3e9d-177b-74f8-a898-c28cbce5680b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019d3e9c-64a9-7e8a-9b82-c60bbaa32436" xlink:to="loc_srt_LitigationCaseAxis_019d3e9d-177b-74f8-a898-c28cbce5680b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019d3e9d-177b-74f8-a898-c28cbce5680b_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019d3e9d-177b-74f8-a898-c28cbce5680b" xlink:to="loc_srt_LitigationCaseTypeDomain_019d3e9d-177b-74f8-a898-c28cbce5680b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019d3e9d-177b-790c-81af-a7e3b4192977" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019d3e9d-177b-74f8-a898-c28cbce5680b" xlink:to="loc_srt_LitigationCaseTypeDomain_019d3e9d-177b-790c-81af-a7e3b4192977" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019d3e9d-177b-7aa6-8c83-83c1ca046a05" xlink:href="q-20260331.xsd#q_ConsentOrderForTheStateOfNewJerseyMattersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019d3e9d-177b-790c-81af-a7e3b4192977" xlink:to="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019d3e9d-177b-7aa6-8c83-83c1ca046a05" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilities_019d3e9c-64a9-7a01-af4e-20a6602682d5" xlink:href="q-20260331.xsd#q_IndemnificationLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_q_IndemnificationLiabilities_019d3e9c-64a9-7a01-af4e-20a6602682d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019d3e9c-64a9-7ad3-a114-93080b77a357" xlink:href="q-20260331.xsd#q_IndemnificationLiabilitiesPotentialMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019d3e9c-64a9-7ad3-a114-93080b77a357" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019d3e9c-64a9-7368-be53-926d16f7e1d1" xlink:href="q-20260331.xsd#q_QualifiedSpendEligiblePFASCostsLifeToDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019d3e9c-64a9-7368-be53-926d16f7e1d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_019d3e9c-64a9-79e8-953b-a2f47aca762e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_019d3e9c-64a9-79e8-953b-a2f47aca762e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019dd1ec-5413-71c2-b31e-ce610fc18ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019dd1ec-5413-71c2-b31e-ce610fc18ff3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ProposedLitigationSettlementPayablePeriod_019dd1ee-5da7-7467-b8dc-47c3539690af" xlink:href="q-20260331.xsd#q_ProposedLitigationSettlementPayablePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_q_ProposedLitigationSettlementPayablePeriod_019dd1ee-5da7-7467-b8dc-47c3539690af" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019d3e9d-177b-71a4-a2c1-2a63a54bed08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_LitigationReserve_019d3e9d-177b-71a4-a2c1-2a63a54bed08" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementInterest_019d3e9d-177b-7e6b-94c0-9986a816017e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LitigationSettlementInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_LitigationSettlementInterest_019d3e9d-177b-7e6b-94c0-9986a816017e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019d3e9d-177b-7905-95f6-00797ac37c07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019d3e9d-177b-7905-95f6-00797ac37c07" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019d3e9d-3d8d-7d2c-a514-14df2b3f3db4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019d3e9c-64a9-790f-b724-b54cdc57553b" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019d3e9d-3d8d-7d2c-a514-14df2b3f3db4" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYNarrativeDetails" xlink:type="simple" xlink:href="q-20260331.xsd#STOCKHOLDERSEQUITYNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019d3eee-a957-735b-8147-ff43242cf42d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019d3eee-a957-735b-8147-ff43242cf42d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019d3eee-a957-73d3-9e96-2c2114953ca7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019d3eee-a957-735b-8147-ff43242cf42d" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019d3eee-a957-73d3-9e96-2c2114953ca7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019d3eee-a957-73d3-9e96-2c2114953ca7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019d3eee-a957-73d3-9e96-2c2114953ca7" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019d3eee-a957-73d3-9e96-2c2114953ca7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019d3eee-a957-77a1-8449-d7c00169eb90" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019d3eee-a957-73d3-9e96-2c2114953ca7" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019d3eee-a957-77a1-8449-d7c00169eb90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_A500MShareAuthorizationMember_019d3eee-a957-7fea-b17e-353b7bdcf183" xlink:href="q-20260331.xsd#q_A500MShareAuthorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019d3eee-a957-77a1-8449-d7c00169eb90" xlink:to="loc_q_A500MShareAuthorizationMember_019d3eee-a957-7fea-b17e-353b7bdcf183" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019d3eee-a957-7120-9b28-cb83843beac6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019d3eee-a957-7120-9b28-cb83843beac6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019e099f-45b5-77e9-9385-c19d32ea044a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019e099f-45b5-77e9-9385-c19d32ea044a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e09a0-6206-75bc-8084-7f9851320165" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e09a0-6206-75bc-8084-7f9851320165" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019d3eee-a957-754a-bbc4-81fb16a5f673" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019d3eee-a957-754a-bbc4-81fb16a5f673" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019dfc70-9481-71f3-a1a0-7f5990eb9039" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019d3eee-a957-7548-9701-629ce8ae58c5" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019dfc70-9481-71f3-a1a0-7f5990eb9039" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="q-20260331.xsd#STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf3a-cd04-7d4d-a21f-8453d8bd7cfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf3a-cd04-70ad-9bc0-bfe0b45abda8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf3a-cd04-7d4d-a21f-8453d8bd7cfe" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf3a-cd04-70ad-9bc0-bfe0b45abda8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cd04-793d-9bb0-52b0d4c298c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019caf3a-cd04-70ad-9bc0-bfe0b45abda8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cd04-793d-9bb0-52b0d4c298c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf3a-cd04-793d-9bb0-52b0d4c298c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cd04-793d-9bb0-52b0d4c298c3" xlink:to="loc_us-gaap_EquityComponentDomain_019caf3a-cd04-793d-9bb0-52b0d4c298c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019caf3a-cd04-704a-88f3-00beb4912375" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019caf3a-cd04-793d-9bb0-52b0d4c298c3" xlink:to="loc_us-gaap_EquityComponentDomain_019caf3a-cd04-704a-88f3-00beb4912375" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cd04-73eb-b6be-0aba622c059a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019caf3a-cd04-704a-88f3-00beb4912375" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cd04-73eb-b6be-0aba622c059a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019caf3a-cd04-70cb-82eb-5e7abc331635" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cd04-73eb-b6be-0aba622c059a" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019caf3a-cd04-70cb-82eb-5e7abc331635" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019caf3a-cd04-78d0-a7f9-ff0f4349c8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019caf3a-cd04-73eb-b6be-0aba622c059a" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019caf3a-cd04-78d0-a7f9-ff0f4349c8bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019caf3a-cd04-7bc7-84f6-e92011df6695" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019caf3a-cd04-7d4d-a21f-8453d8bd7cfe" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019caf3a-cd04-7bc7-84f6-e92011df6695" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cd04-7bcb-8d06-b3491d694b93" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019caf3a-cd04-7bc7-84f6-e92011df6695" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cd04-7bcb-8d06-b3491d694b93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019db845-323c-7fe1-b3a8-8e731c9cbccd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019caf3a-cd04-7bc7-84f6-e92011df6695" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019db845-323c-7fe1-b3a8-8e731c9cbccd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019caf3a-cd04-760d-9976-3ed72f7f6c98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKBASEDCOMPENSATIONDetails" xlink:type="simple" xlink:href="q-20260331.xsd#STOCKBASEDCOMPENSATIONDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKBASEDCOMPENSATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019caf3a-cd04-7ec3-8dfa-4bb743801bdd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019caf3a-cd04-7ec3-8dfa-4bb743801bdd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019caf3a-cd04-70f5-b224-d7cca2df94df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019caf3a-cd04-7ec3-8dfa-4bb743801bdd" xlink:to="loc_us-gaap_PlanNameAxis_019caf3a-cd04-70f5-b224-d7cca2df94df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019caf3a-cd04-70f5-b224-d7cca2df94df_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019caf3a-cd04-70f5-b224-d7cca2df94df" xlink:to="loc_us-gaap_PlanNameDomain_019caf3a-cd04-70f5-b224-d7cca2df94df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019caf3a-cd04-7dd0-a852-95a8cbcf4393" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019caf3a-cd04-70f5-b224-d7cca2df94df" xlink:to="loc_us-gaap_PlanNameDomain_019caf3a-cd04-7dd0-a852-95a8cbcf4393" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_QnityElectronicsInc.EquityAndIncentivePlanMember_019d3f06-e610-7443-a853-4d50c94f0f61" xlink:href="q-20260331.xsd#q_QnityElectronicsInc.EquityAndIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019caf3a-cd04-7dd0-a852-95a8cbcf4393" xlink:to="loc_q_QnityElectronicsInc.EquityAndIncentivePlanMember_019d3f06-e610-7443-a853-4d50c94f0f61" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019caf3a-cd04-7976-be96-71a1dac96b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019caf3a-cd04-7ec3-8dfa-4bb743801bdd" xlink:to="loc_us-gaap_AwardTypeAxis_019caf3a-cd04-7976-be96-71a1dac96b3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7976-be96-71a1dac96b3d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019caf3a-cd04-7976-be96-71a1dac96b3d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7976-be96-71a1dac96b3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7149-a333-2b1ff2ecef44" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019caf3a-cd04-7976-be96-71a1dac96b3d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7149-a333-2b1ff2ecef44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019caf3a-cd04-797a-a0b9-c187c9cfb10a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7149-a333-2b1ff2ecef44" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019caf3a-cd04-797a-a0b9-c187c9cfb10a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019caf3a-cd04-726c-88c7-b86e6cc7455f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019caf3a-cd04-7149-a333-2b1ff2ecef44" xlink:to="loc_us-gaap_PerformanceSharesMember_019caf3a-cd04-726c-88c7-b86e6cc7455f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019caf3a-cd04-77ce-b8aa-4b8cee30a092" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019caf3a-cd04-77ce-b8aa-4b8cee30a092" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019caf3a-cd04-73f4-a090-49fa2363119a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019caf3a-cd04-73f4-a090-49fa2363119a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_019caf3a-cd04-7548-8c11-692df12332e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_019caf3a-cd04-7548-8c11-692df12332e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019caf3a-cd04-7693-bb00-c70e7424c0b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019caf3a-cd04-7693-bb00-c70e7424c0b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019caf3a-cd04-744c-9821-5f7d08d5dd96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019caf3a-cd04-7671-8f7a-fec4f8430d4d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019caf3a-cd04-744c-9821-5f7d08d5dd96" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="q-20260331.xsd#FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf3a-cd04-75e9-b914-44605c19b120" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf3a-cd04-7734-a7b2-44382fa2ffd6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf3a-cd04-75e9-b914-44605c19b120" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf3a-cd04-7734-a7b2-44382fa2ffd6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-764b-8ccf-b9cadd8df2fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019caf3a-cd04-7734-a7b2-44382fa2ffd6" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-764b-8ccf-b9cadd8df2fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-764b-8ccf-b9cadd8df2fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-764b-8ccf-b9cadd8df2fa" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-764b-8ccf-b9cadd8df2fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-725a-80d6-0b02e4f90c56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-764b-8ccf-b9cadd8df2fa" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-725a-80d6-0b02e4f90c56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-7e26-9557-7a288d55613d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-725a-80d6-0b02e4f90c56" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-7e26-9557-7a288d55613d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsAtCarryingValue_019caf3a-cd04-7658-aa60-63d3057c3a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf3a-cd04-75e9-b914-44605c19b120" xlink:to="loc_us-gaap_CashEquivalentsAtCarryingValue_019caf3a-cd04-7658-aa60-63d3057c3a1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019caf3a-cd04-75e9-b914-44605c19b120" xlink:to="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019caf3a-cd04-7238-9a5a-d052e26e7793" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:to="loc_us-gaap_DerivativeAssets_019caf3a-cd04-7238-9a5a-d052e26e7793" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax_019caf3a-cd04-7e43-b624-7b9128175831" xlink:href="q-20260331.xsd#q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:to="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax_019caf3a-cd04-7e43-b624-7b9128175831" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax_019caf3a-cd04-7d5a-ac0b-ffa07f2609fc" xlink:href="q-20260331.xsd#q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:to="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax_019caf3a-cd04-7d5a-ac0b-ffa07f2609fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019caf3a-cd04-7832-ac11-64c0a80cba83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019caf3a-cd04-73f8-a4f5-e5e74da636d6" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019caf3a-cd04-7832-ac11-64c0a80cba83" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails" xlink:type="simple" xlink:href="q-20260331.xsd#FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019caf3a-cd04-7ce2-a559-f05a325ff9ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019caf3a-cd04-7126-a9fa-b9c27381da29" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019caf3a-cd04-7ce2-a559-f05a325ff9ce" xlink:to="loc_us-gaap_DerivativeTable_019caf3a-cd04-7126-a9fa-b9c27381da29" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-754f-95c1-bdc100d1b115" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019caf3a-cd04-7126-a9fa-b9c27381da29" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-754f-95c1-bdc100d1b115" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-754f-95c1-bdc100d1b115_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-754f-95c1-bdc100d1b115" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-754f-95c1-bdc100d1b115_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-754d-92b1-dafc3224f0b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-754f-95c1-bdc100d1b115" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-754d-92b1-dafc3224f0b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019caf3a-cd04-7d44-901a-bd1058c80e30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-754d-92b1-dafc3224f0b4" xlink:to="loc_us-gaap_NondesignatedMember_019caf3a-cd04-7d44-901a-bd1058c80e30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-7481-9a74-8bace809ca47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019caf3a-cd04-7126-a9fa-b9c27381da29" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-7481-9a74-8bace809ca47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7481-9a74-8bace809ca47_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-7481-9a74-8bace809ca47" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7481-9a74-8bace809ca47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7612-ba00-429107abd802" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-7481-9a74-8bace809ca47" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7612-ba00-429107abd802" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-7823-a6ab-dded58021a35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7612-ba00-429107abd802" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-7823-a6ab-dded58021a35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeNotionalAmountNet_019caf3a-cd04-70f8-91a8-f0f631fe4c25" xlink:href="q-20260331.xsd#q_DerivativeNotionalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019caf3a-cd04-7ce2-a559-f05a325ff9ce" xlink:to="loc_q_DerivativeNotionalAmountNet_019caf3a-cd04-70f8-91a8-f0f631fe4c25" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="simple" xlink:href="q-20260331.xsd#FINANCIALINSTRUMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019caf3a-cdb7-7b04-bb50-1ca09c1d34e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf3a-cd04-7934-bfaa-37b8f32b5670" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf3a-cdb7-7b04-bb50-1ca09c1d34e0" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf3a-cd04-7934-bfaa-37b8f32b5670" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-7b8d-aae7-f6c9506f52ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf3a-cd04-7934-bfaa-37b8f32b5670" xlink:to="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-7b8d-aae7-f6c9506f52ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-7b8d-aae7-f6c9506f52ea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-7b8d-aae7-f6c9506f52ea" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-7b8d-aae7-f6c9506f52ea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-71cb-aabf-3849ba865317" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019caf3a-cd04-7b8d-aae7-f6c9506f52ea" xlink:to="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-71cb-aabf-3849ba865317" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019caf3a-cd04-78bf-aacb-df26b00bc534" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019caf3a-cd04-71cb-aabf-3849ba865317" xlink:to="loc_us-gaap_NondesignatedMember_019caf3a-cd04-78bf-aacb-df26b00bc534" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-771d-9f5c-33a652fbe0c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019caf3a-cd04-7934-bfaa-37b8f32b5670" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-771d-9f5c-33a652fbe0c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-771d-9f5c-33a652fbe0c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-771d-9f5c-33a652fbe0c5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-771d-9f5c-33a652fbe0c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7995-b6b8-da8dd7d5172b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cd04-771d-9f5c-33a652fbe0c5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7995-b6b8-da8dd7d5172b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-79be-b74f-067cd4f0d779" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cd04-7995-b6b8-da8dd7d5172b" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cd04-79be-b74f-067cd4f0d779" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019caf3a-cdb7-7b20-98db-52c82f025716" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019caf3a-cdb7-7b04-bb50-1ca09c1d34e0" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019caf3a-cdb7-7b20-98db-52c82f025716" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="simple" xlink:href="q-20260331.xsd#FAIRVALUEMEASUREMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf3a-cdb7-739e-888d-a55516c763d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf3a-cdb7-739e-888d-a55516c763d7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf3a-cdb7-7577-97ec-4a19710168fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf3a-cdb7-739e-888d-a55516c763d7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf3a-cdb7-7577-97ec-4a19710168fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf3a-cdb7-7577-97ec-4a19710168fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf3a-cdb7-7577-97ec-4a19710168fc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf3a-cdb7-7577-97ec-4a19710168fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf3a-cdb7-76a0-bb17-2738b41e3633" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019caf3a-cdb7-7577-97ec-4a19710168fc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf3a-cdb7-76a0-bb17-2738b41e3633" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019caf3a-cdb7-7e1d-8e2d-1b352c7c6c1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019caf3a-cdb7-76a0-bb17-2738b41e3633" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019caf3a-cdb7-7e1d-8e2d-1b352c7c6c1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cdb7-7a9e-9425-3f20cee022b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019caf3a-cdb7-739e-888d-a55516c763d7" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cdb7-7a9e-9425-3f20cee022b7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cdb7-7a9e-9425-3f20cee022b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cdb7-7a9e-9425-3f20cee022b7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cdb7-7a9e-9425-3f20cee022b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cdb7-79cd-99dc-75556ac82950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019caf3a-cdb7-7a9e-9425-3f20cee022b7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cdb7-79cd-99dc-75556ac82950" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cdb7-7d04-a625-4a39274bbc7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019caf3a-cdb7-79cd-99dc-75556ac82950" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019caf3a-cdb7-7d04-a625-4a39274bbc7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf3a-cdb7-7f1a-b157-ea9ed8c77115" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf3a-cdb7-7f1a-b157-ea9ed8c77115" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019caf3a-cdb7-7f0a-8d25-014ca11bdfd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf3a-cdb7-7f1a-b157-ea9ed8c77115" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019caf3a-cdb7-7f0a-8d25-014ca11bdfd1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019caf3a-cdb7-7c7f-9cd8-8768e13dca5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf3a-cdb7-7f1a-b157-ea9ed8c77115" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019caf3a-cdb7-7c7f-9cd8-8768e13dca5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019caf3a-cdb7-7b58-8c17-e6679c6311f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019caf3a-cdb7-7f1a-b157-ea9ed8c77115" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019caf3a-cdb7-7b58-8c17-e6679c6311f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf3a-cdb7-78ed-b6f6-45fe50b83b17" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf3a-cdb7-78ed-b6f6-45fe50b83b17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019caf3a-cdb7-7c09-9762-f8af15ea4970" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf3a-cdb7-78ed-b6f6-45fe50b83b17" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019caf3a-cdb7-7c09-9762-f8af15ea4970" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019caf3a-cdb7-7e9f-9384-3502fca207bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019caf3a-cdb7-78ed-b6f6-45fe50b83b17" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019caf3a-cdb7-7e9f-9384-3502fca207bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019caf3a-cdb7-76df-9932-5577ad778a53" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:to="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019caf3a-cdb7-76df-9932-5577ad778a53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019caf3a-cdb7-7742-8590-c5e0d671d7d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019caf3a-cdb7-7b20-8658-ca5757f86ee4" xlink:to="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019caf3a-cdb7-7742-8590-c5e0d671d7d3" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails" xlink:type="simple" xlink:href="q-20260331.xsd#SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-74fb-a531-f301bfaa98c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-74fb-a531-f301bfaa98c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7c8d-98f4-2e07a287365f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-74fb-a531-f301bfaa98c1" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7c8d-98f4-2e07a287365f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7c8d-98f4-2e07a287365f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7c8d-98f4-2e07a287365f" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7c8d-98f4-2e07a287365f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-73f3-857f-308a85f5f194" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7c8d-98f4-2e07a287365f" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-73f3-857f-308a85f5f194" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-75d2-bd24-f1b042331739" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-73f3-857f-308a85f5f194" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-75d2-bd24-f1b042331739" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7da6-a3ba-64c373f9d9ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-74fb-a531-f301bfaa98c1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7da6-a3ba-64c373f9d9ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7da6-a3ba-64c373f9d9ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7da6-a3ba-64c373f9d9ef" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7da6-a3ba-64c373f9d9ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7ada-9360-6d9a3aa58cd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7da6-a3ba-64c373f9d9ef" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7ada-9360-6d9a3aa58cd1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019d3f19-ee4a-7317-ad8e-d49a95b537d1" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7ada-9360-6d9a3aa58cd1" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019d3f19-ee4a-7317-ad8e-d49a95b537d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019d3f19-ee4a-761a-aa55-b787709f92a8" xlink:href="q-20260331.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7ada-9360-6d9a3aa58cd1" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019d3f19-ee4a-761a-aa55-b787709f92a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax_019caf3a-cd04-7b1e-a03e-a70566c2a82a" xlink:href="q-20260331.xsd#q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax_019caf3a-cd04-7b1e-a03e-a70566c2a82a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentCostOfGoodsAndServicesSold_019caf3a-cd04-7108-ad45-cf4ce51b59de" xlink:href="q-20260331.xsd#q_SegmentCostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentCostOfGoodsAndServicesSold_019caf3a-cd04-7108-ad45-cf4ce51b59de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentSellingGeneralAndAdministrativeExpense_019caf3a-cd04-74dd-a7b5-d2f16c728fb1" xlink:href="q-20260331.xsd#q_SegmentSellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentSellingGeneralAndAdministrativeExpense_019caf3a-cd04-74dd-a7b5-d2f16c728fb1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentResearchAndDevelopmentExpense_019caf3a-cd04-7e0f-9781-371bf70250b0" xlink:href="q-20260331.xsd#q_SegmentResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentResearchAndDevelopmentExpense_019caf3a-cd04-7e0f-9781-371bf70250b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems_019caf3a-cd04-7ec5-8a93-4c438e192c3d" xlink:href="q-20260331.xsd#q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems_019caf3a-cd04-7ec5-8a93-4c438e192c3d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019caf3a-cd04-7ce4-a973-bdf66548ceb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019caf3a-cd04-7ce4-a973-bdf66548ceb6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentDepreciationAndAmortization_019caf3a-cd04-7329-8569-edb9b49ae7cf" xlink:href="q-20260331.xsd#q_SegmentDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_SegmentDepreciationAndAmortization_019caf3a-cd04-7329-8569-edb9b49ae7cf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019caf3a-cd04-7f1d-a3b7-991e162a1b78" xlink:href="q-20260331.xsd#q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c81-b456-89fcca843d38" xlink:to="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019caf3a-cd04-7f1d-a3b7-991e162a1b78" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails" xlink:type="simple" xlink:href="q-20260331.xsd#SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-7f4b-a107-869bfb2160c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-7f4b-a107-869bfb2160c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-7f4b-a107-869bfb2160c8" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7ad9-bb0e-e962f112ba84" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7bc5-b9b4-d0d33c10fdde" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7ad9-bb0e-e962f112ba84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7762-acaf-c4c6341f550c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7ad9-bb0e-e962f112ba84" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7762-acaf-c4c6341f550c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-764f-84b9-4c7c0cbc9463" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7ad9-bb0e-e962f112ba84" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-764f-84b9-4c7c0cbc9463" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7113-951f-c5cc95b003ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-7f4b-a107-869bfb2160c8" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7113-951f-c5cc95b003ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7113-951f-c5cc95b003ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7113-951f-c5cc95b003ee" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7113-951f-c5cc95b003ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c1e-9315-212954e79438" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7113-951f-c5cc95b003ee" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c1e-9315-212954e79438" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019d3f1e-8264-7e99-8f90-61747243086e" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c1e-9315-212954e79438" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019d3f1e-8264-7e99-8f90-61747243086e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019d3f1e-8264-7098-8eac-51d9556a393a" xlink:href="q-20260331.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7c1e-9315-212954e79438" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019d3f1e-8264-7098-8eac-51d9556a393a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019caf3a-cd04-7c18-a831-d6600e272017" xlink:href="q-20260331.xsd#q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019caf3a-cd04-7c18-a831-d6600e272017" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019caf3a-cd04-7364-a481-35b07fadad3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019caf3a-cd04-7364-a481-35b07fadad3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit_019d3f1f-4956-7085-8ba1-35ee1823133e" xlink:href="q-20260331.xsd#q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit_019d3f1f-4956-7085-8ba1-35ee1823133e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense_019caf3a-cd04-7e7d-b4c1-4155adf2dd1a" xlink:href="q-20260331.xsd#q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense_019caf3a-cd04-7e7d-b4c1-4155adf2dd1a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_019caf3a-cd04-7801-b24b-a3342d8cca86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionAndOtherPostretirementBenefitExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_019caf3a-cd04-7801-b24b-a3342d8cca86" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems_019caf3a-cd04-7ec9-b94d-960fe2c64d79" xlink:href="q-20260331.xsd#q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems_019caf3a-cd04-7ec9-b94d-960fe2c64d79" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture_019d3f1f-9a3c-7b63-92f3-a48aa93faec6" xlink:href="q-20260331.xsd#q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture_019d3f1f-9a3c-7b63-92f3-a48aa93faec6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonrecurringIncomeExpense_019caf3a-cd04-7b90-b7b9-18282a5f312d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonrecurringIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_us-gaap_OtherNonrecurringIncomeExpense_019caf3a-cd04-7b90-b7b9-18282a5f312d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019caf3a-cd04-7ea1-98f8-7ba61bd12359" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-71c1-8875-411405e2840c" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019caf3a-cd04-7ea1-98f8-7ba61bd12359" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails" xlink:type="simple" xlink:href="q-20260331.xsd#SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7a18-9025-76985e65daaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-71b6-adf1-f16b2b2fe960" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7a18-9025-76985e65daaf" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-71b6-adf1-f16b2b2fe960" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-75f7-958b-5c56d62bf930" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-71b6-adf1-f16b2b2fe960" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-75f7-958b-5c56d62bf930" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-75f7-958b-5c56d62bf930_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-75f7-958b-5c56d62bf930" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-75f7-958b-5c56d62bf930_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7a2e-90a8-75771d097a4e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-75f7-958b-5c56d62bf930" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7a2e-90a8-75771d097a4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7408-9a05-a56101617597" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7a2e-90a8-75771d097a4e" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7408-9a05-a56101617597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-7267-bb5e-03a7e3d768ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7a2e-90a8-75771d097a4e" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-7267-bb5e-03a7e3d768ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b28-b3eb-83ac8f720b15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-71b6-adf1-f16b2b2fe960" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b28-b3eb-83ac8f720b15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7b28-b3eb-83ac8f720b15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b28-b3eb-83ac8f720b15" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7b28-b3eb-83ac8f720b15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7109-8c06-0956985c5e75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b28-b3eb-83ac8f720b15" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7109-8c06-0956985c5e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019d3f25-5e6f-75a8-9205-c841142841e4" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7109-8c06-0956985c5e75" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019d3f25-5e6f-75a8-9205-c841142841e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019d3f25-5e6f-79a1-ba7e-9677f3cdf054" xlink:href="q-20260331.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7109-8c06-0956985c5e75" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019d3f25-5e6f-79a1-ba7e-9677f3cdf054" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationIntegrationAndOtherCharges_019e0467-3c62-780a-8b61-ca318eee4615" xlink:href="q-20260331.xsd#q_TransformationIntegrationAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7a18-9025-76985e65daaf" xlink:to="loc_q_TransformationIntegrationAndOtherCharges_019e0467-3c62-780a-8b61-ca318eee4615" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EmployeeRetentionCredit_019caf3a-cd04-7f04-ad2f-7e763c04c4e5" xlink:href="q-20260331.xsd#q_EmployeeRetentionCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7a18-9025-76985e65daaf" xlink:to="loc_q_EmployeeRetentionCredit_019caf3a-cd04-7f04-ad2f-7e763c04c4e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonrecurringIncomeExpense_019caf3a-cd04-705b-90ed-caec454fd3ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonrecurringIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7a18-9025-76985e65daaf" xlink:to="loc_us-gaap_OtherNonrecurringIncomeExpense_019caf3a-cd04-705b-90ed-caec454fd3ef" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails" xlink:type="simple" xlink:href="q-20260331.xsd#SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c28-8d63-fec1dc353627" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-72a3-a51a-7dc507140a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c28-8d63-fec1dc353627" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-72a3-a51a-7dc507140a7d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7cca-91fc-10b32eed9c27" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-72a3-a51a-7dc507140a7d" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7cca-91fc-10b32eed9c27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7cca-91fc-10b32eed9c27_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7cca-91fc-10b32eed9c27" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7cca-91fc-10b32eed9c27_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-757e-9063-b3792fc458b8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7cca-91fc-10b32eed9c27" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-757e-9063-b3792fc458b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-735b-8172-2152a8e66867" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-757e-9063-b3792fc458b8" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-735b-8172-2152a8e66867" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-7b75-a4be-77a6c6523200" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-757e-9063-b3792fc458b8" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-7b75-a4be-77a6c6523200" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b58-b7e1-2db6e827768b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-72a3-a51a-7dc507140a7d" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b58-b7e1-2db6e827768b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7b58-b7e1-2db6e827768b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b58-b7e1-2db6e827768b" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7b58-b7e1-2db6e827768b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-730d-8115-7ae55a685bf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-7b58-b7e1-2db6e827768b" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-730d-8115-7ae55a685bf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019d3f28-bd10-72a2-8540-06d95f97b2bd" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-730d-8115-7ae55a685bf5" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019d3f28-bd10-72a2-8540-06d95f97b2bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019d3f28-bd10-7667-a24b-ab4cb9b32674" xlink:href="q-20260331.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-730d-8115-7ae55a685bf5" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019d3f28-bd10-7667-a24b-ab4cb9b32674" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019caf3a-cd04-747e-ae9e-5e34e5d6b656" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c28-8d63-fec1dc353627" xlink:to="loc_us-gaap_Assets_019caf3a-cd04-747e-ae9e-5e34e5d6b656" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019caf3a-cd04-73c6-9a6e-301d943b86ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7c28-8d63-fec1dc353627" xlink:to="loc_us-gaap_EquityMethodInvestments_019caf3a-cd04-73c6-9a6e-301d943b86ef" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails" xlink:type="simple" xlink:href="q-20260331.xsd#SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7cf0-b7b4-49bbe839d812" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-715e-87ab-6c4f709c926f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7cf0-b7b4-49bbe839d812" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-715e-87ab-6c4f709c926f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7f09-aa23-bcdd01c6c587" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-715e-87ab-6c4f709c926f" xlink:to="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7f09-aa23-bcdd01c6c587" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7f09-aa23-bcdd01c6c587_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7f09-aa23-bcdd01c6c587" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7f09-aa23-bcdd01c6c587_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7d20-94be-816b9224ee0d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019caf3a-cd04-7f09-aa23-bcdd01c6c587" xlink:to="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7d20-94be-816b9224ee0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7a0a-8ef6-2af05572db07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7d20-94be-816b9224ee0d" xlink:to="loc_us-gaap_OperatingSegmentsMember_019caf3a-cd04-7a0a-8ef6-2af05572db07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-79db-a499-6b63cce649f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019caf3a-cd04-7d20-94be-816b9224ee0d" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019caf3a-cd04-79db-a499-6b63cce649f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-746f-b81a-30abd719d2bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019caf3a-cd04-715e-87ab-6c4f709c926f" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-746f-b81a-30abd719d2bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-746f-b81a-30abd719d2bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-746f-b81a-30abd719d2bc" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-746f-b81a-30abd719d2bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019caf3a-cd04-7a14-bedb-e9a91c3c69d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019caf3a-cd04-746f-b81a-30abd719d2bc" xlink:to="loc_us-gaap_SegmentDomain_019caf3a-cd04-7a14-bedb-e9a91c3c69d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019d3f2c-66bc-7e05-8e60-444c6396cd4b" xlink:href="q-20260331.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7a14-bedb-e9a91c3c69d9" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019d3f2c-66bc-7e05-8e60-444c6396cd4b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019d3f2c-a879-7364-af8b-1098f8787949" xlink:href="q-20260331.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019caf3a-cd04-7a14-bedb-e9a91c3c69d9" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019d3f2c-a879-7364-af8b-1098f8787949" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019caf3a-cd04-7cf0-8626-baf993618e40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7cf0-b7b4-49bbe839d812" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019caf3a-cd04-7cf0-8626-baf993618e40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures_019caf3a-cd04-7d83-8a98-f999837e2597" xlink:href="q-20260331.xsd#q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7cf0-b7b4-49bbe839d812" xlink:to="loc_q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures_019caf3a-cd04-7d83-8a98-f999837e2597" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ExpenditureAdditionToLongLivedAssetsNet_019caf3a-cd04-70e8-b823-10836fbcea6a" xlink:href="q-20260331.xsd#q_ExpenditureAdditionToLongLivedAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019caf3a-cd04-7cf0-b7b4-49bbe839d812" xlink:to="loc_q_ExpenditureAdditionToLongLivedAssetsNet_019caf3a-cd04-70e8-b823-10836fbcea6a" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
