<SEC-DOCUMENT>0001243786-17-000058.txt : 20170313
<SEC-HEADER>0001243786-17-000058.hdr.sgml : 20170313
<ACCEPTANCE-DATETIME>20170313120859
ACCESSION NUMBER:		0001243786-17-000058
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170307
FILED AS OF DATE:		20170313
DATE AS OF CHANGE:		20170313

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MOSAIC CO
		CENTRAL INDEX KEY:			0001285785
		STANDARD INDUSTRIAL CLASSIFICATION:	AGRICULTURE CHEMICALS [2870]
		IRS NUMBER:				201026454
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		3033 CAMPUS DRIVE, SUITE E490
		CITY:			PLYMOUTH
		STATE:			MN
		ZIP:			55441
		BUSINESS PHONE:		7635772700

	MAIL ADDRESS:	
		STREET 1:		3033 CAMPUS DRIVE, SUITE E490
		CITY:			PLYMOUTH
		STATE:			MN
		ZIP:			55441

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	GLOBAL NUTRITION SOLUTIONS INC
		DATE OF NAME CHANGE:	20040401

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			McLellan Richard N
		CENTRAL INDEX KEY:			0001397354

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32327
		FILM NUMBER:		17684490

	MAIL ADDRESS:	
		STREET 1:		THE MOSAIC COMPANY
		STREET 2:		3033 CAMPUS DRIVE SUITE E490
		CITY:			PLYMOUTH
		STATE:			MN
		ZIP:			55441
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>wf-form4a_148942132585961.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2017-03-07</periodOfReport>

    <dateOfOriginalSubmission>2017-03-09</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001285785</issuerCik>
        <issuerName>MOSAIC CO</issuerName>
        <issuerTradingSymbol>MOS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001397354</rptOwnerCik>
            <rptOwnerName>McLellan Richard N</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O THE MOSAIC COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>3033 CAMPUS DRIVE, SUITE E490</rptOwnerStreet2>
            <rptOwnerCity>PLYMOUTH</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55441</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr Vice President-Brazil</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-03-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5428</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>29.18</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>63304</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares sold to cover tax liability incurred as a result of most recent vesting of restricted stock and performance units.</footnote>
        <footnote id="F2">The exact number of shares sold to cover tax liability incurred as a result of the most recent vesting of Restricted Stock Units and Performance Units was estimated at the time the original Form 4 was filed.  The reporting person is hereby amending this line item to correct an administrative error which resulted in an overstatement of the shares sold and reflect the final calculation of the number of shares withheld to satisfy reporting person's tax obligations.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark J. Isaacson, Attorney in Fact for Richard N. McLellan</signatureName>
        <signatureDate>2017-03-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
