As filed with the Securities and Exchange Commission on August 5, 2025

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Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-8

REGISTRATION STATEMENT

Under the Securities Act of 1933

TRANSOCEAN LTD.

(Exact Name of Registrant as Specified in its Charter)

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AMENDED AND RESTATED TRANSOCEAN LTD. 2015 LONG-TERM INCENTIVE PLAN

(Full title of plan)

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Brady K. Long

Executive Vice President and Chief Legal Officer

Transocean Ltd.

c/o Transocean Offshore Deepwater Drilling Inc.

1414 Enclave Parkway

Houston, Texas 77077

+1 (713) 232-7500

(Name, Address and Telephone Number, Including Area Code, of Agent for Service)

Copy to:

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James B. Marshall

Baker Botts L.L.P.

910 Louisiana Street

Houston, Texas 77002-4995

(713) 229-1234

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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REGISTRATION OF ADDITIONAL SECURITIES

This Registration Statement is being filed by Transocean Ltd., a Swiss corporation (the “Company” or the “Registrant”) pursuant to General Instruction E of Form S-8 under the Securities Act of 1933, as amended, to register an additional 16,000,000 registered shares pursuant to the Amended and Restated Transocean Ltd. 2015 Long-Term Incentive Plan (as amended to date, the “Plan”).

The Board of Directors of the Company recommended for approval and, on May 30, 2025, shareholders of the Company approved, an amendment of the Plan that increased the number of shares authorized for issuance under the Plan from 138,361,451 to 154,361,451 shares.

The contents of the Registration Statements on Form S-8 filed with the U.S. Securities and Exchange Commission (the “Commission”) on May 21, 2015 (No. 333-204359), October 9, 2018 (No. 333-227750), May 8, 2020 (No. 333-238091), July 9, 2021 (No. 333-257804), June 16, 2023 (No. 333-272734) and June 28, 2024, as amended on July 5, 2024 (No. 333-280610), are incorporated by reference into this Registration Statement, except as amended hereby.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 8. Exhibits.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Steinhausen, Switzerland, on August 5, 2025.

TRANSOCEAN LTD.


By: /s/ Keelan I. Adamson

Name: Keelan I. Adamson

Title: President and Chief Executive Officer

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POWER OF ATTORNEY

Each person whose signature appears below constitutes and appoints Keelan I. Adamson, R. Thaddeus Vayda and Brady K. Long, and each of them, his or her true and lawful attorneys-in-fact and agents, with full power to act separately and full power of substitution and re-substitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement and all additional registration statements pursuant to Rule 462(b) of the Securities Act of 1933, and to file the same, with all exhibits thereto, and all other documents in connection therewith, with the Commission, granting unto each said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite or necessary to be done in connection therewith, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or either of them, or his or her or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities indicated below on August 5, 2025.

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Exhibit 5.1

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Transocean Ltd.

Registration Statement on Form S-8

We have acted as special Swiss counsel to Transocean Ltd., a company limited by shares incorporated under the laws of Switzerland (the Company), in connection with the Registration Statement on Form S-8 (the Registration Statement) to be filed with the United States Securities and Exchange Commission (the SEC) on the date hereof under the Securities Act of 1933, as amended (the Act), with respect to the registration of an additional 16,000,000 registered shares of the Company, each with a nominal value of USD 0.10, that may be delivered pursuant to the Plan (as defined below).

As such counsel, we have been requested to give our opinion as to certain legal matters under Swiss law.

Capitalized terms used herein shall have the meaning attributed to them in the Documents unless otherwise defined herein. The Company's registered shares, each with a nominal value of USD 0.10, are referred to herein as Registered Shares.

This opinion is confined to and given on the basis of the laws of Switzerland in force at the date hereof as currently applied by the Swiss courts. In the absence of explicit statutory law, we base our opinion solely on our independent professional judgment. This opinion is also confined to the matters stated herein and is not to be read as extending, by implication or otherwise, to any document referred to in the Documents (other than listed below) or any other matter.

For purposes of this opinion, we have not conducted any due diligence or similar investigation as to factual circumstances which are or may be referred to in the Documents, and we express no opinion as to the accuracy of representations and warranties of facts set out in the Documents or the factual background assumed therein.

For the purpose of giving this opinion, we have only reviewed originals or copies of the following documents (collectively the Documents):

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(the AGM), as reflected in the minutes of such meeting, dated May 30, 2025, regarding the approval by the Company's shareholders of, among other things, the reserve of an additional 16,000,000 Registered Shares in the aggregate amount of Registered Shares available for issuance pursuant to the Amended and Restated Transocean Ltd. 2015 Long-Term Incentive Plan (the Plan);

No documents have been reviewed by us in connection with this opinion other than those listed above. Accordingly, we shall limit our opinion to the Documents and their legal implications under Swiss law.

In this opinion, Swiss legal concepts are expressed in English terms and not in their original language. These concepts may not be identical to the concepts described by the same English terms as they exist under the laws of other jurisdictions.

In rendering the opinion below, we have assumed the following:

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Based on the foregoing and subject to the qualifications set out below, we are of the opinion that:

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Registered Shares have been validly issued, fully paid up to their nominal value and are non-assessable.

The above opinions are subject to the following qualifications:

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We have issued this opinion as of the date hereof and we assume no obligation to advise you of any changes that are made or brought to our attention hereafter.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act.

This opinion is governed by and shall be construed in accordance with the laws of Switzerland.

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Sincerely yours,
HOMBURGER AG

/s/ David Oser​ ​
David Oser

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

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We consent to the incorporation by reference in the Registration Statement on Form S-8 pertaining to the Amended and Restated Transocean Ltd. 2015 Long-Term Incentive Plan of our reports dated February 18, 2025, with respect to the consolidated financial statements and schedule of Transocean Ltd. and subsidiaries and the effectiveness of internal control over financial reporting of Transocean Ltd. and subsidiaries, included in its Annual Report (Form 10-K) for the year ended December 31, 2024, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

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Houston, Texas
August 5, 2025

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