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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0206 </schemaVersion> |
| <documentType> 3 </documentType> |
| <periodOfReport> 2017-08-18 </periodOfReport> |
| <noSecuritiesOwned> 0 </noSecuritiesOwned> |
| <issuer> |
| | <issuerCik> 0001552033 </issuerCik> |
| | <issuerName> TransUnion </issuerName> |
| | <issuerTradingSymbol> TRU </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001714465 </rptOwnerCik> |
| | | <rptOwnerName> Cello Todd M </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> C/O TRANSUNION </rptOwnerStreet1> |
| | | <rptOwnerStreet2> 555 WEST ADAMS STREET </rptOwnerStreet2> |
| | | <rptOwnerCity> CHICAGO </rptOwnerCity> |
| | | <rptOwnerState> IL </rptOwnerState> |
| | | <rptOwnerZipCode> 60661 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 0 </isDirector> |
| | | <isOfficer> 1 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle> EVP & CFO </officerTitle> |
| | | <otherText></otherText> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeHolding> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 10692 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeHolding> |
| | </nonDerivativeTable> |
| <derivativeTable> |
| | <derivativeHolding> |
| | | <securityTitle> |
| <value> Stock Options (right to buy) </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <value> 4.99 </value> |
| </conversionOrExercisePrice> |
| | | <exerciseDate> |
| <footnoteId id="F1"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <value> 2022-08-01 </value> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 5893.0 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </derivativeHolding> |
| | <derivativeHolding> |
| | | <securityTitle> |
| <value> Stock Options (right to buy) </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <value> 22.5 </value> |
| </conversionOrExercisePrice> |
| | | <exerciseDate> |
| <footnoteId id="F2"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <value> 2025-06-24 </value> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 7200.0 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </derivativeHolding> |
| | </derivativeTable> |
| <footnotes> |
| | <footnote id="F1"> Represents an initial grant of 58,918 stock options, 40% of which vest upon the attainment of time-based vesting criteria and 60% of which vest upon the attainment of both time-based and performance-based vesting criteria. The performance-based vesting criteria was satisfied on February 22, 2017, and all options now follow the time-based vesting criteria as follows: 20% on the first anniversary of the date of grant and 5% on the last day of each subsequent full calendar quarter. </footnote> |
| | <footnote id="F2"> Represents an initial grant of 10,000 stock options, 40% of which vest upon the attainment of time-based vesting criteria and 60% of which vest upon the attainment of both time-based and performance-based vesting criteria. The performance-based vesting criteria was satisfied on February 22, 2017, and all options now follow the time-based vesting criteria as follows: 20% on the first anniversary of the date of grant and 5% on the last day of each subsequent full calendar quarter. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> /s/ Michael J. Forde, by power of attorney </signatureName> |
| | <signatureDate> 2017-08-21 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |