越洋钻探美股招股说明书(2025-09-26版)

Transocean Ltd. 125,000,000 Shares We are offering to sell 125,000,000 of our shares, par value $0.10 (“shares”). Our shares are listed on the New York Stock Exchange (“NYSE”) under the symbol “RIG.” The last reported sale price of ourshares on the NYSE on September 22, 2025 was $3.39 per share. (1) Please read “Underwriting (Conflicts of Interest)” for additional information regarding underwriting compensation. An affiliate of one of our directors, Frederik Mohn, has provided an indication of interest in purchasing up to an aggregate of4,000,000 shares from the underwriters at the public offering price.The number of our shares available for sale to the public willbe reduced to the extent such person purchases such shares. The underwriters will not receive any underwriting discounts orcommissions on any shares sold to any affiliate of Frederik Mohn. The indication of interest is not a commitment to purchase,and such person is not obligated to purchase any of our shares in this offering. Please read “Underwriting” for additionalinformation. We have granted the underwriters an option for a period of 30 days to purchase up to an additional 18,750,000 of our shares atthe public offering price, less underwriting discounts and commissions. INVESTING IN OUR SHARES INVOLVES RISKS.PLEASE READ THE “RISK FACTORS” ON PAGE S-4 OF THISPROSPECTUSSUPPLEMENT AND THE“RISK FACTORS”SECTION BEGINNING ON PAGE 9 OF OURANNUAL REPORTON FORM 10-K FOR THE YEAR ENDED DECEMBER 31,2024,PAGE 24 OF OURQUARTERLY REPORT ON FORM 10-Q FOR THE QUARTERLY PERIOD ENDED MARCH 31, 2025AND PAGE 24OF OURQUARTERLY REPORT ON FORM 10-Q FOR THE QUARTERLY PERIOD ENDED JUNE 30, 2025,WHICHARE INCORPORATED BY REFERENCE INTO THIS PROSPECTUS SUPPLEMENT AND THEACCOMPANYINGBASE PROSPECTUS CONCERNING FACTORS YOU SHOULD CONSIDER BEFOREINVESTING IN OUR SHARES. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus supplement and the accompanying base prospectus are truthful orcomplete.Any representation to the contrary is a criminal offense. The underwriters expect to deliver the shares on or about September 26, 2025.____________________ Morgan StanleyWells FargoSecurities CitigroupDNB Carnegie Goldman Sachs & Co.LLC Co-Managers Standard Bank SB1 Markets TABLE OF CONTENTS PROSPECTUS SUPPLEMENTABOUT THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING BASEPROSPECTUSS-iiFORWARD-LOOKING INFORMATIONS-iiiSUMMARYS-1THE OFFERINGS-2RISK FACTORSS-4USE OF PROCEEDSS-6DESCRIPTION OF TRANSOCEAN LTD. SHARESS-7MATERIAL TAX CONSEQUENCESS-18UNDERWRITING (CONFLICTS OF INTEREST)S-27LEGAL MATTERSS-35EXPERTSS-35WHERE YOU CAN FIND MORE INFORMATIONS-35INCORPORATION BY REFERENCES-36 ABOUT THIS PROSPECTUSiiFORWARD-LOOKING INFORMATIONiiiENFORCEABILITY OF CIVIL LIABILITIES AGAINST FOREIGN PERSONS1ABOUT TRANSOCEAN LTD.2ABOUT TRANSOCEAN INC.2WHERE YOU CAN FIND MORE INFORMATION2INCORPORATION BY REFERENCE3RISK FACTORS3USE OF PROCEEDS4DESCRIPTION OF TRANSOCEAN INC. DEBT SECURITIES AND TRANSOCEAN LTD.GUARANTEE5DESCRIPTION OF TRANSOCEAN LTD. SHARES13DESCRIPTION OF WARRANTS24DESCRIPTION OF PURCHASE CONTRACTS26DESCRIPTION OF RIGHTS27DESCRIPTION OF UNITS28ANTI-TAKEOVER PROVISIONS29PLAN OF DISTRIBUTION31VALIDITY OF THE SECURITIES34EXPERTS35 ABOUT THIS PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING BASEPROSPECTUS This document consists of two parts.The first part is the prospectus supplement, which describes thespecific terms of this offering and also adds to and updates the information contained or incorporatedby reference in the accompanying base prospectus.The second part is the accompanying baseprospectus, which describes more general information regarding our securities, some of which doesnot apply to this offering.If the information varies between this prospectus supplement and theaccompanying base prospectus, you should rely on the information in this prospectus supplement. Any statement made in this prospectus, any free writing prospectus authorized by us or in a documentincorporated by reference into this prospectus will be deemed to be modified or superseded forpurposes of this prospectus to the extent that a statement contained in this prospectus, any free writingprospectus authorized by us or in any other subsequently filed document that is also incorporated byreference into this prospectus modifies or supersedes that statement. Any statement so modified orsuperseded will not be deemed, except as so modified or superseded, to constitute a part of thisprospectus. Please read “Incorporation by Reference.” We have not authorized anyone to provide you with any information other than the informationcontained in this prospectus supplement or the accompanying base prospectus prepared by or onbehalf of us or incorporated by reference into this prospectus supplement or the accompanyingbase prospectus.Neither we nor the underwriters take any responsibility for, nor can we or theunde