<SEC-DOCUMENT>0000913760-18-000078.txt : 20180515
<SEC-HEADER>0000913760-18-000078.hdr.sgml : 20180515
<ACCEPTANCE-DATETIME>20180515192353
ACCESSION NUMBER:		0000913760-18-000078
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180511
FILED AS OF DATE:		20180515
DATE AS OF CHANGE:		20180515

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Lyon Charles M
		CENTRAL INDEX KEY:			0001620576

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36045
		FILM NUMBER:		18838418

	MAIL ADDRESS:	
		STREET 1:		329 PARK AVENUE NORTH
		STREET 2:		SUITE 350
		CITY:			WINTER PARK
		STATE:			FL
		ZIP:			32789

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			INTL FCSTONE INC.
		CENTRAL INDEX KEY:			0000913760
		STANDARD INDUSTRIAL CLASSIFICATION:	SECURITY & COMMODITY BROKERS, DEALERS, EXCHANGES & SERVICES [6200]
		IRS NUMBER:				592921318
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		708 THIRD AVENUE
		STREET 2:		SUITE 1500
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017
		BUSINESS PHONE:		212-485-3500

	MAIL ADDRESS:	
		STREET 1:		708 THIRD AVENUE
		STREET 2:		SUITE 1500
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	INTERNATIONAL ASSETS HOLDING CORP
		DATE OF NAME CHANGE:	19931020
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_152642656910284.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-05-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000913760</issuerCik>
        <issuerName>INTL FCSTONE INC.</issuerName>
        <issuerTradingSymbol>INTL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001620576</rptOwnerCik>
            <rptOwnerName>Lyon Charles M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>329 PARK AVENUE NORTH</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 350</rptOwnerStreet2>
            <rptOwnerCity>WINTER PARK</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>32789</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Executive VP - subsidiary</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-05-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>19622</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>46.5747</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19950</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported represents an average price.  The Reporting Person will provide to the Commission, the issuer and any stockholder, upon request, full information regarding the number of shares sold at each separate price.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Charles M. Lyon</signatureName>
        <signatureDate>2018-05-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
