Transocean Ltd.

​ Commission file number 001-38373 ​ ​ TRANSOCEAN LTD . (Exact name of registrant as specified in its charter) ​ ​ ​ Switzerland 98-0599916 (State or other jurisdiction of incorporation or organization) (I.R.S. Employer Identification No.) ​ ​ Turmstrasse 30 ​ Steinhausen , Switzerland 6312 (Address of principal executive offices) (Zip Code)

TRANSOCEAN LTD. AND SUBSIDIARIES INDEX TO ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED DECEMBER 31, 2025 ​ Item ​ Page PART I Item 1. Business 2 Item 1A. Risk Factors 8 Item 1B. Unresolved Staff Comments 22 Item 1C. Cybersecurity 22 Item 2. Properties 23 Item 3. Legal Proceedings 23 Item 4. Mine Safety Disclosures 24 ​ ​ ​ PART II Item 5. Market for Registrant's Common Equity, Related Shareholder Matters and Issuer Purchases of Equity Securities 24 Item 6. Reserved 26 Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations 26 Item 7A. Quantitative and Qualitative Disclosures About Market Risk 36 Item 8. Financial Statements and Supplementary Data 37 Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure 70 Item 9A. Controls and Procedures 70 Item 9B. Other Information 70 Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections 70 ​ ​ ​ PART III Item 10. Directors, Executive Officers and Corporate Governance 70 Item 11. Executive Compensation 70 Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Shareholder Matters 70 Item 13. Certain Relationships and Related Transactions, and Director Independence 70 Item 14. Principal Accountant Fees and Services 70 ​ ​ ​ PART IV Item 15. Exhibits and Financial Statement Schedules 71 ​ ​ ​

Forward-Looking Information The statements included in this annual report regarding future financial performance and results of operations and other statements that are not historical facts are forward-looking statements within the meaning of Section 27A of the United States ("U.S.") Securities Act of 1933 and Section 21E of the U.S. Securities Exchange Act of 1934. Forward-looking statements in this annual report include, but are not limited to, statements about the following subjects: ◾ the effect of any disputes and actions with respect to production levels by, among or between major oil and gas producing countries and any expectations we may have with respect thereto;

◾ our results of operations, our cash flow from operations, our revenue efficiency and other performance indicators and optimization of rig-based spending ;

◾ the offshore drilling market, including the effects of variations in commodity prices, supply and demand, utilization rates, dayrates, customer drilling programs, customer strategy, stacking and reactivation of rigs, the impact of changes to regulations in jurisdictions in which we operate and changes in the global economy or market outlook for our industry or the various geographies in which we operate;

◾ customer drilling contracts, including contract backlog, force majeure provisions, contract awards, commencements, extensions, cancellations, terminations, renegotiations, contract option exercises, contract revenues, early termination fees, indemnity provisions and rig mobilizations;

◾ the addition of renewable or other energy alternatives to meet local, regional or global demand for energy and efforts by us or our customers, to reduce greenhouse gas emissions or operating intensity thereof;

◾ liquidity, including availability under our Secured Credit Facility, as defined in this annual report, and adequacy of cash flows for our obligations;

◾ debt, including interest rates, credit ratings and our evaluation or decisions with respect to any potential liability management transactions or strategic alternatives intended to prudently manage our liquidity, debt maturities and other aspects of our capital structure and any litigation, potential or alleged defaults and discussions with creditors related thereto;

◾ upgrade, shipyard, reactivations and other capital projects, including the level of expected capital expenditures and the timing and cost of completing capital projects, relinquishment or abandonment, expected downtime and lost revenues;

◾ the cost and timing of acquisitions and reactivations, and the proceeds and timing of dispositions;

◾ our expectations regarding the timing, completion and anticipated benefits of the proposed business combination (the "Business Combination") with Valaris Limited, an exempted company limited by shares incorporated under the laws of Bermuda ("Valaris");

◾ tax matters, including our effective tax rate, uncertain tax positions, changes in tax laws, treaties and regulations, tax assessments, tax incentive programs and liabilities for tax issues in the tax jurisdictions in which we operate or have a taxable presence;

◾ legal and regulatory matters, including results and effects of current or potential legal proceedings and governmental audits and assessments, outcomes and effects of internal and governmental investigations, customs and environmental matters;

◾ insurance matters, risk tolerance and risk response, including adequacy and solvency of insurance, renewal of insurance, insurance proceeds and cash investments of our wholly owned captive insurance company;

◾ effects of accounting changes and adoption of accounting policies; and

◾ investment in recruitment, retention and personnel development initiatives, the timing of, and other matters concerning, severance payments, benefit payments and maintaining agreements with labor unions .

Forward-looking statements in this annual report are identifiable by use of the following words and other similar expressions: ◾

Such statements are subject to numerous risks, uncertainties and assumptions, including, but not limited to: ◾ those described under "Item 1A. Risk Factors" in this annual report on Form 10-K;

◾ the effects of actions by, or disputes among or between, members of the Organization of the Petroleum Exporting Countries and other oil and natural gas producing countries with respect to production levels or other matters related to the prices of oil and natural gas;

◾ the adequacy of and access to our sources of liquidity;

◾ our inability to renew drilling contracts at comparable, or improved, dayrates and to obtain drilling contracts for our rigs that do not have contracts;

◾ the cancellation of drilling contracts currently included in our reported contract backlog;

◾ losses on impairment of long-lived assets;

◾ the results of meetings of our shareholders;

◾ changes in political, social and economic conditions, including the effects of political and military disputes;

◾ the possibility of changes in tax, environmental, trade, immigration and other laws, regulations and policies, including the imposition of tariffs, economic or trade sanctions or other trade barriers and actions of government that impact, whether directly or indirectly, oil and gas operations;

◾ the effect and results of litigation, regulatory matters, settlements, audits, assessments and contingencies;

◾ the availability of borrowings under our Secured Credit Facility, as defined below, as well as the timing of any amendments thereto; and

The foregoing risks and uncertainties are beyond our ability to control, and in many cases, we cannot predict the risks and uncertainties that could cause our actual results to differ materially from those indicated by the forward-looking statements. Should one or more of these risks or uncertainties materialize, or should underlying assumptions prove incorrect, actual results may vary materially from those indicated. All subsequent written and oral forward-looking statements attributable to us or to persons acting on our behalf are expressly qualified in their entirety by reference to these risks and uncertainties. You should not place undue reliance on forward-looking statements, each of which speaks only as of the date of the particular statement. We expressly disclaim any obligations or undertaking to release publicly any updates or revisions to any forward-looking statement to reflect any change in our expectations or beliefs with regard to the statement or any change in events, conditions or circumstances on which any forward-looking statement is based, except as required by law.

PART I Item 1. Business Overview Transocean Ltd. (together with its subsidiaries and predecessors, unless the context requires otherwise, "Transocean,"the"Company," "we," "us"or"our") is a leading international provider of offshore contract drilling services for oil and gas wells. As of February 17, 2026, we owned or had partial ownership interests in and operated 27 mobile offshore drilling units, consisting of 20 ultra-deepwater drillships and seven harsh environment semisubmersibles. We provide, as our primary business, contract drilling services in a single operating segment, which involves contracting our mobile offshore drilling rigs, related equipment and work crews to drill oil and gas wells. We specialize in technically demanding regions of the global offshore drilling business with a particular focus on ultra-deepwater and harsh environment drilling services. Our drilling fleet is one of the most versatile fleets in the world, consisting of drillships and semisubmersible floaters used in support of offshore drilling activities and offshore support services on a worldwide basis. Transocean Ltd. is a Swiss corporation with its registered office in Steinhausen, Canton of Zug, and with principal executive offices located at Turmstrasse 30, 6312 Steinhausen, Switzerland. Our telephone number at that address is +41 41 749-0500. Our shares are listed on the New York Stock Exchange under the ticker symbol "RIG." On February 9, 2026, we and Valaris entered into a Business Combination Agreement (the "Agreement") providing for the Business Combination. Pursuant to the Agreement, and on the terms and subject to the conditions thereof, we will acquire all of the issued and outstanding common shares, par value $0.01 each, of Valaris (the "Valaris Shares") in exchange for Transocean Ltd. shares, par value $0.10 each, at an exchange ratio of 15.235 Transocean Ltd. shares for each Valaris Share. For information about the revenues, operating income, assets and other information related to our business, our agreement to acquire of Valaris, and the geographic areas in which we operate, see " Part II. Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations "and"Part II. Item 8. Financial Statements and Supplementary Data - Notes to Consolidated Financial Statements - Note 1 - Business , Note 5 - Revenues and Note 6 - Long-Lived Assets ." Drilling Fleet Overview - We provide contract drilling services using our fleet of mobile offshore drilling units, including both drillships and semisubmersibles, broadly referred to as floaters. Floaters are designed to operate in locations away from port for extended periods of time and have living quarters for the crews, a helicopter landing deck and storage space for drill pipe, riser and drilling supplies. Our drilling units and related equipment are suitable for both exploration and development, and we engage in both types of activities. Our fleet of floaters consists of ultra-deepwater drillships and harsh environment semisubmersibles that are designed with high-specification capabilities to operate in the technically demanding regions of the global offshore drilling business. Ultra-deepwater floaters are equipped with high-pressure mud pumps and are capable of drilling in water depths of 4,500 feet or greater. Harsh environment floaters are capable of drilling in harsh environments in water depths between 1,500 and 10,000 feet and typically have greater displacement than other semisubmersibles, which offers larger variable load capacity, more useable deck space and better motion characteristics. Drillship features - Drillships are floating vessels that are shaped like conventional ships, generally self-propelled and considered to be the most mobile of the major rig types. Drillships typically have greater deck load and storage capacity than semisubmersible rigs, which provides logistical and resupply efficiency benefits for customers. Drillships are generally better suited to operations in calmer sea conditions and typically do not operate in areas considered to be harsh environments. All of our high-specification drillships are equipped with dynamic positioning thruster systems, which allows them to maintain position without anchors through the use of onboard propulsion and station-keeping systems. We have two drillships that are equipped with an industry-leading, 1,700 short ton hoisting capacity. We have 18 drillships that are equipped with dual-activity technology that employs structures, equipment and techniques using two drilling stations within a dual derrick to allow these drillships to perform simultaneous drilling tasks in a parallel, rather than a sequential manner, which reduces critical path activity and improves efficiency in both exploration and development drilling. Semisubmersible features - Semisubmersibles are floating vessels that can be partially submerged by means of a water ballast system such that the lower column sections and pontoons are below the water surface during drilling operations. Semisubmersibles are known for stability, making them well suited for operating in rough sea conditions. Semisubmersible floaters are capable of maintaining their position over a well either through dynamic positioning or the use of mooring systems. Although most semisubmersibles are relocated with the assistance of tugs, some units are self-propelled and move between locations under their own power when afloat on pontoons. All of our semisubmersibles have mooring capability and are equipped for year-round operations in harsh environments, such as those of the Norwegian continental shelf and sub-Arctic waters. Two of our seven semisubmersibles are custom-designed, high-capacity drilling rigs, equipped with dual-activity technology. Fleet status - Depending on market conditions, we may idle or stack our non-contracted rigs. An idle rig is between drilling contracts, readily available for operations, and operating costs are typically at or near normal operating levels. A stacked rig typically has

reduced operating and maintenance costs, is staffed by a reduced crew or has no crew and is (a) preparing for an extended period of inactivity, (b) expected to continue to be inactive for an extended period or (c) completing a period of extended inactivity. Stacked rigs will continue to incur operating costs at or above normal operating levels for approximately 30 days following initiation of stacking. Some idle rigs and all stacked rigs require additional costs to return to service. The actual cost to return to service, which in many instances could be significant and could fluctuate over time, depends upon various factors, including the availability and cost of shipyard facilities, the cost of equipment and materials, the extent of repairs, maintenance and commercial upgrades that may ultimately be required, the length of time a rig has spent in stacking mode and the time and cost of assembling and training crew. We consider these