<SEC-DOCUMENT>0001451505-15-000082.txt : 20150519
<SEC-HEADER>0001451505-15-000082.hdr.sgml : 20150519
<ACCEPTANCE-DATETIME>20150519150621
ACCESSION NUMBER:		0001451505-15-000082
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150515
FILED AS OF DATE:		20150519
DATE AS OF CHANGE:		20150519

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Transocean Ltd.
		CENTRAL INDEX KEY:			0001451505
		STANDARD INDUSTRIAL CLASSIFICATION:	DRILLING OIL & GAS WELLS [1381]
		IRS NUMBER:				980599916
		STATE OF INCORPORATION:			V8
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		BLANDONNET INTERNATIONAL BUSINESS CENTER
		STREET 2:		BLDG F, 7TH FLOOR, CHEMIN DE BLANDONNET
		CITY:			VERNIER
		STATE:			V8
		ZIP:			1214
		BUSINESS PHONE:		41-58-792-9243

	MAIL ADDRESS:	
		STREET 1:		BLANDONNET INTERNATIONAL BUSINESS CENTER
		STREET 2:		BLDG F, 7TH FLOOR, CHEMIN DE BLANDONNET
		CITY:			VERNIER
		STATE:			V8
		ZIP:			1214

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MCNAMARA MARTIN B
		CENTRAL INDEX KEY:			0001040104

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-53533
		FILM NUMBER:		15876135

	MAIL ADDRESS:	
		STREET 1:		4 GREENWAY PLAZA
		STREET 2:		PO BOX 2765 77252-2765
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77046
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_143206237126579.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-05-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001451505</issuerCik>
        <issuerName>Transocean Ltd.</issuerName>
        <issuerTradingSymbol>RIG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001040104</rptOwnerCik>
            <rptOwnerName>MCNAMARA MARTIN B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 CHEMIN DE BLANDONNET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>VERNIER</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>1214</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-05-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10836</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Registered Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10836.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10836</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Deferred Units, which are 1-for-1 registered share equivalents, were acquired on May 15, 2015 pursuant to the issuer's long-term incentive plan. Deferred Units vest on the earlier of: (i) May 15, 2016; or (ii) the date of the next Annual General Meeting of the Company's shareholders following the May 15, 2015 grant date.  Pursuant to the award agreement, such Deferred Units will be payable in registered shares of the issuer following the vesting date, as defined above.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Jill S. Greene, by Power of Attorney</signatureName>
        <signatureDate>2015-05-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
