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<?xml version="1.0" encoding="windows-1252"?> |
<ownershipDocument> |
| <schemaVersion> X0306 </schemaVersion> |
| <documentType> 4 </documentType> |
| <periodOfReport> 2022-09-13 </periodOfReport> |
| <notSubjectToSection16> 0 </notSubjectToSection16> |
| <issuer> |
| | <issuerCik> 0001285785 </issuerCik> |
| | <issuerName> MOSAIC CO </issuerName> |
| | <issuerTradingSymbol> MOS </issuerTradingSymbol> |
| | </issuer> |
| <reportingOwner> |
| | <reportingOwnerId> |
| | | <rptOwnerCik> 0001186942 </rptOwnerCik> |
| | | <rptOwnerName> EBEL GREGORY L </rptOwnerName> |
| | | </reportingOwnerId> |
| | <reportingOwnerAddress> |
| | | <rptOwnerStreet1> C/O THE MOSAIC COMPANY </rptOwnerStreet1> |
| | | <rptOwnerStreet2> 101 EAST KENNEDY BLVD., SUITE 2500 </rptOwnerStreet2> |
| | | <rptOwnerCity> TAMPA </rptOwnerCity> |
| | | <rptOwnerState> FL </rptOwnerState> |
| | | <rptOwnerZipCode> 33602 </rptOwnerZipCode> |
| | | <rptOwnerStateDescription></rptOwnerStateDescription> |
| | | </reportingOwnerAddress> |
| | <reportingOwnerRelationship> |
| | | <isDirector> 1 </isDirector> |
| | | <isOfficer> 0 </isOfficer> |
| | | <isTenPercentOwner> 0 </isTenPercentOwner> |
| | | <isOther> 0 </isOther> |
| | | <officerTitle></officerTitle> |
| | | <otherText></otherText> |
| | | </reportingOwnerRelationship> |
| | </reportingOwner> |
| <nonDerivativeTable> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-09-13 </value> |
| </transactionDate> |
| | | <transactionCoding> |
| <transactionFormType> 5 </transactionFormType> |
| <transactionCode> G </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| <footnoteId id="F1"/> |
| </transactionCoding> |
| | | <transactionTimeliness> |
| <value> E </value> |
| </transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 30000 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 0 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> D </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 62094 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | <nonDerivativeTransaction> |
| | | <securityTitle> |
| <value> Common Stock </value> |
| </securityTitle> |
| | | <transactionDate> |
| <value> 2022-09-13 </value> |
| </transactionDate> |
| | | <transactionCoding> |
| <transactionFormType> 5 </transactionFormType> |
| <transactionCode> G </transactionCode> |
| <equitySwapInvolved> 0 </equitySwapInvolved> |
| <footnoteId id="F1"/> |
| </transactionCoding> |
| | | <transactionTimeliness> |
| <value> E </value> |
| </transactionTimeliness> |
| | | <transactionAmounts> |
| <transactionShares> |
| <value> 30000 </value> |
| </transactionShares> |
| <transactionPricePerShare> |
| <value> 0 </value> |
| </transactionPricePerShare> |
| <transactionAcquiredDisposedCode> |
| <value> A </value> |
| </transactionAcquiredDisposedCode> |
| </transactionAmounts> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 30000 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> I </value> |
| </directOrIndirectOwnership> |
| <natureOfOwnership> |
| <value> 2022 Annuity Trust I dated September 13, 2022 </value> |
| </natureOfOwnership> |
| </ownershipNature> |
| | | </nonDerivativeTransaction> |
| | </nonDerivativeTable> |
| <derivativeTable> |
| | <derivativeHolding> |
| | | <securityTitle> |
| <value> Restricted Stock Units </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <value> 0.0 </value> |
| <footnoteId id="F2"/> |
| </conversionOrExercisePrice> |
| | | <exerciseDate> |
| <footnoteId id="F3"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <footnoteId id="F4"/> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 22511.0 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 22511 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </derivativeHolding> |
| | <derivativeHolding> |
| | | <securityTitle> |
| <value> Restricted Stock Units </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <value> 0.0 </value> |
| <footnoteId id="F2"/> |
| </conversionOrExercisePrice> |
| | | <exerciseDate> |
| <footnoteId id="F5"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <footnoteId id="F4"/> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 7439.0 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 7439 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </derivativeHolding> |
| | <derivativeHolding> |
| | | <securityTitle> |
| <value> Restricted Stock Units </value> |
| </securityTitle> |
| | | <conversionOrExercisePrice> |
| <value> 0.0 </value> |
| <footnoteId id="F2"/> |
| </conversionOrExercisePrice> |
| | | <exerciseDate> |
| <footnoteId id="F6"/> |
| </exerciseDate> |
| | | <expirationDate> |
| <footnoteId id="F4"/> |
| </expirationDate> |
| | | <underlyingSecurity> |
| <underlyingSecurityTitle> |
| <value> Common Stock </value> |
| </underlyingSecurityTitle> |
| <underlyingSecurityShares> |
| <value> 4291.0 </value> |
| </underlyingSecurityShares> |
| </underlyingSecurity> |
| | | <postTransactionAmounts> |
| <sharesOwnedFollowingTransaction> |
| <value> 4291 </value> |
| </sharesOwnedFollowingTransaction> |
| </postTransactionAmounts> |
| | | <ownershipNature> |
| <directOrIndirectOwnership> |
| <value> D </value> |
| </directOrIndirectOwnership> |
| </ownershipNature> |
| | | </derivativeHolding> |
| | </derivativeTable> |
| <footnotes> |
| | <footnote id="F1"> This transaction involved a gift of issuer's common stock by the reporting person to a grantor retained annuity trust dated September 13, 2022, for the benefit of reporting person and his children ("2022 Annuity Trust I"). The reporting person serves as trustee of the 2022 Annuity Trust I. </footnote> |
| | <footnote id="F2"> One-for-One </footnote> |
| | <footnote id="F3"> The restricted stock units vested on the date of the issuer's 2021 Annual Meeting of Stockholders. Vested shares will be delivered to the reporting person on May 21, 2023. </footnote> |
| | <footnote id="F4"> Not Applicable </footnote> |
| | <footnote id="F5"> The restricted stock units vested on the date of the issuer's 2022 Annual Meeting of Stockholders. Vested shares will be delivered to the reporting person on May 20, 2024. </footnote> |
| | <footnote id="F6"> The restricted stock units will vest and be paid to the reporting person on the later of (i) the date of the issuer's 2023 Annual Meeting of Stockholders; or (ii) the date that is at 50 weeks after the issuer's immediately preceding year's annual meeting. </footnote> |
| | </footnotes> |
| <remarks></remarks> |
| <ownerSignature> |
| | <signatureName> /s/ Mark J. Isaacson, Attorney-in-Fact for Gregory L. Ebel </signatureName> |
| | <signatureDate> 2022-09-14 </signatureDate> |
| | </ownerSignature> |
| </ownershipDocument> |