<SEC-DOCUMENT>0000846913-17-000108.txt : 20171218
<SEC-HEADER>0000846913-17-000108.hdr.sgml : 20171218
<ACCEPTANCE-DATETIME>20171218162607
ACCESSION NUMBER:		0000846913-17-000108
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20171215
FILED AS OF DATE:		20171218
DATE AS OF CHANGE:		20171218

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Pach James M
		CENTRAL INDEX KEY:			0001722648

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33059
		FILM NUMBER:		171261682

	MAIL ADDRESS:	
		STREET 1:		27601 BELLA VISTA PARKWAY
		CITY:			WARRENVILLE
		STATE:			IL
		ZIP:			60555

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FUEL TECH, INC.
		CENTRAL INDEX KEY:			0000846913
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL & COMMERCIAL FANS & BLOWERS & AIR PURIFYING EQUIP [3564]
		IRS NUMBER:				205657551
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		27601 BELLA VISTA PARKWAY
		CITY:			WARRENVILLE
		STATE:			IL
		ZIP:			60555
		BUSINESS PHONE:		6308454433

	MAIL ADDRESS:	
		STREET 1:		27601 BELLA VISTA PARKWAY
		CITY:			WARRENVILLE
		STATE:			IL
		ZIP:			60555

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	FUEL TECH N V
		DATE OF NAME CHANGE:	19930510
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_151363235310853.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-12-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000846913</issuerCik>
        <issuerName>FUEL TECH, INC.</issuerName>
        <issuerTradingSymbol>FTEK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001722648</rptOwnerCik>
            <rptOwnerName>Pach James M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>27601 BELLA VISTA PARKWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WARRENVILLE</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60555</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Acting PFO &amp; Treasurer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-12-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>50000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>50000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>56859</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each Restricted Stock Unit represents a contingent right to receive one stock of FTEK Common Stock.</footnote>
        <footnote id="F2">The Restricted Stock Units vest in two installments: (i) one half of the total RSUs awarded shall vest on the second anniversary after the transaction date shown above, and (ii) the final one half shall vest on the third anniversary of the transaction date shown above. Subject to the restrictions on distribution set forth in the registrant's 2017 RSU Award Agreement, generally, shares will be delivered to the reporting person in respect of vested RSUs as soon as practicable after each vesting date, unless the reporting person has elected to defer distribution until a later date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>James M. Pach</signatureName>
        <signatureDate>2017-12-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
