明晟美股招股说明书(2025-10-31版)

We are offering $500,000,000 aggregate principal amount of our 5.150% Senior Notes due 2036 (the “Notes”). We will pay interest on the Notes on March 15andSeptember 15 of each year, beginning on March 15, 2026. The Notes will mature on March15, 2036. We may redeem the Notes in whole or in part at any time or from time to time at the redemption prices described under “Description of Notes—Optional Redemption.”Upon a Change of Control Repurchase Event, we may be required to make an offer to repurchase all outstanding Notes as described under “Description of Notes—Change ofControl Repurchase Event.” The Notes will be our senior unsecured obligations. The Notes will rank equally in right of payment to all of our existing and future senior unsubordinated debt, includingour 4.000% senior unsecured notes due 2029 (the “2029 Senior Notes”), our 3.625% senior unsecured notes due 2030 (the “2030 Senior Notes”), our 3.875% senior unsecurednotes due 2031 (the “3.875% 2031 Senior Notes”), our 3.625% senior unsecured notes due 2031 (the “3.625% 2031 Senior Notes”), our 3.250% senior unsecured notes due 2033(the “2033 Senior Notes”) and our 5.250% senior unsecured notes due 2035 (the “2035 Senior Notes” and, collectively with the 2029 Senior Notes, the 2030 Senior Notes, the3.875% 2031 Senior Notes, the 3.625% 2031 Senior Notes and the 2033 Senior Notes, the “Senior Notes”) and any obligations outstanding under the Revolving Credit Facility (asdefined herein), and rank senior to all of our future subordinated debt. The Notes will be effectively junior to all of our future secured debt to the extent of the value of the collateralsecuring such secured debt and will be structurally subordinated to all of the existing and future indebtedness (including trade payables) of our subsidiaries (other than indebtednessand liabilities owed to us, if any). Investing in the Notes involves risks. See the sections entitled “Risk Factors” beginning on pageS-6of this prospectus supplement and in our Annual Report onForm10-Kfor the year ended December31, 2024, which is incorporated by reference into this prospectus supplement and the accompanying prospectus. PerNoteTotalPublic offering price(1)99.650%$498,250,000Underwriting discount0.650%$3,250,000Proceeds (before expenses and commissions)(1)99.000%$495,000,000 (1)Plus accrued interest, if any, from November 6, 2025, if settlement occurs after that date. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if thisprospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The Notes will be ready for delivery in book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, includingEuroclear Bank S.A./N.V. and Clearstream Banking,société anonyme, on or about November6, 2025, which will be the fifth business day following the date of this prospectussupplement (such settlement being referred to as “T+5”). Pursuant to Rule15c6-1under the Exchange Act, trades in the secondary market generally are required to settle in onebusiness day unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers of the Notes who wish to trade the Notes prior to the first business daypreceding the settlement date will be required, by virtue of the fact that the Notes initially will settle in T+5, to specify an alternative settlement cycle at the time of any such tradeto prevent failed settlement and should consult their own advisors. Joint Book-Running Managers BofASecuritiesMorganStanleyTD Securities J.P.MorganGoldmanSachs&Co.LLCCitizens Capital Markets RBCCapitalMarkets Co-Managers M&TSecurities Scotiabank CreditAgricoleCIB Table of Contents We have not authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus supplement,the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We take noresponsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. This prospectus supplement andthe accompanying prospectus are an offer to sell only the Notes, but only under circumstances and in jurisdictions where it is lawful to do so. Theinformation contained in this prospectus supplement, the accompanying prospectus or in any free writing prospectus, as well as information previouslyfiled with the Securities and Exchange Commission (“SEC”) and incorporated herein by reference, is current only as of the date of such information.Our business, financial condition, results of operations and prospects may have changed since that date. References in this prospectus supplement and the accompanying prospectus to the “Company,” “MSCI,” “we,” “us,” and “our” refer to MSCI Inc.and its subsid