<SEC-DOCUMENT>0000913760-18-000091.txt : 20180613
<SEC-HEADER>0000913760-18-000091.hdr.sgml : 20180613
<ACCEPTANCE-DATETIME>20180613163649
ACCESSION NUMBER:		0000913760-18-000091
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180613
FILED AS OF DATE:		20180613
DATE AS OF CHANGE:		20180613

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Nguyen Xuong
		CENTRAL INDEX KEY:			0001575484

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36045
		FILM NUMBER:		18897104

	MAIL ADDRESS:	
		STREET 1:		230 SOUTH LASALLE
		STREET 2:		SUITE 10-500
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60604

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_152892219204646.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001575484</rptOwnerCik>
            <rptOwnerName>Nguyen Xuong</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>230 SOUTH LASALLE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 10-500</rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60604</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Operating Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2018-06-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.5027</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>22548</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>Xuong Nguyen</signatureName>
        <signatureDate>2018-06-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
