艾奇资本美股招股说明书(2026-06-02版)

Subject to CompletionPreliminary Prospectus Supplement dated June 2, 2026 The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the Arch Capital Group Ltd.$ % Senior Notes due 2036$ % Senior Notes due 2056 Arch Capital Group Ltd. (the “issuer”) is offering $aggregate principal amount of% senior notes due 2036 (the “ 2036 notes”) and$aggregate principal amount of% senior notes due 2056 (the “2056 notes” and, together with the 2036 notes, the “notes”). The issuer will payinterest on the notes semi-annually onandof each year, beginning on, 2026. The 2036 notes will mature on,2036 and the 2056 notes matureon, 2056. The maturity date of the notes may be deferred in certain circumstances as described under the caption “Description of Notes—Principal, Interestand Maturity.” The issuer may redeem some or all of the notes at any time at the applicable redemption prices described under the caption “Description of Notes—Optional Redemption.”The issuer may also redeem all of the Notes under the circumstances described under the heading “Description of Notes—Redemptionfor Tax Purposes.”Notwithstanding the foregoing, the notes will not be redeemable at any time, including at any applicable maturity date, unless the Conditions The issuer intends to use the net proceeds from this offering to redeem, repurchase, repay or otherwise retire the 2026 Existing Notes (as defined herein)and finance the Tender Offers (as defined herein). Any net proceeds not used for the foregoing will be used for general corporate purposes. See “Use of The notes will be senior unsecured obligations of the issuer, will rank equally with any of the issuer’s senior unsecured and unsubordinated indebtednessfrom time to time outstanding, be senior in right of payment to our future indebtedness that is expressly subordinated in right of payment to the notes, beeffectively subordinated to all secured indebtedness of the issuer to the extent of the value of the assets securing such indebtedness; be effectively subordinated An investment in the notes involves risks. See “Risk Factors” beginning on pageS-10of this prospectus supplement to read about important factors youshould consider before investing in the notes. None of the Securities and Exchange Commission, the Bermuda Monetary Authority, the Registrar of Companies in Bermuda, or any statesecurities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectusare truthful or complete. Any representation to the contrary is a criminal offense. (1)Plus accrued interest, if any, from , 2026 if settlement occurs after that date.The underwriters expect to deliver the notes in book-entry form only through the facilities of The Depository Trust Company (“DTC”) against paymentin New York, New York on or about,2026. Active Joint Book-Running Managers Lloyds Securities Wells Fargo Securities The date of this prospectus supplement is, 2026. Prospectus Supplement About This Prospectus SupplementS-1Prospectus Supplement SummaryS-4Risk FactorsS-10 ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering,including risk factors and material tax considerations, and also adds to and updates information contained in the accompanyingprospectus and the documents incorporated by reference herein. The second part is the accompanying prospectus, which gives moregeneral information, some of which may not apply to this offering. It is important for you to read and consider all informationcontained in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein in makingyour investment decision. To fully understand this offering, you should also read all of these documents, including our Annual Report You should rely only on the information contained or incorporated by reference in this prospectus supplement and theaccompanying prospectus. We have not, and the underwriters have not, authorized any other person to provide you with differentinformation. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and theunderwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should In this prospectus supplement and in the accompanying prospectus, except as otherwise noted or the context requires otherwise:(a) “ACGL” or “issuer” refers to Arch Capital Group Ltd., (b) “Arch Finance” refers to our 100% owned U.S. subsidiary, Arch CapitalFinance LLC, (c) “we,” “us,” “our,” “Arch” and “the Company” refer to ACGL and its subsidiaries and (d) “Arch Re Bermuda” refers Unless otherwise indicated, all amounts are expressed in U.S. dollars and all references to “$” and “dollars” mean U.S. dollars.Certain m