AMG资管美股招股说明书(2025-12-10版)

AFFILIATED MANAGERS GROUP, INC. 5.500% Senior Notes due 2036 We are offering $425,000,000 aggregate principal amount of 5.500% senior notes due 2036, which we refer to in this prospectus supplement as the notes. We will pay interest on the notes on February 15 and August 15 of each year, beginning August 15, 2026. The notes will be issued only in registered form inminimum denominations of $2,000 and in integral multiples of $1,000 in excess thereof. The notes will mature on February 15, 2036. We may redeem the notes, in whole or in part, at any time and from time to time at the redemption prices described under “Description of Notes—OptionalRedemption of Notes.” If a change of control repurchase event occurs, we may be required to offer to purchase the notes from the holders as described in thisprospectus supplement under the heading “Description of Notes—Offer to Repurchase Upon a Change of Control Repurchase Event.” We do not intend to list the notes on any securities exchange or to arrange for the notes to be quoted on any quotation system. Currently, there is no publicmarket for the notes. The notes will be our general unsecured and unsubordinated obligations and will rank equally in right of payment with all our other unsubordinated obligationsfrom time to time outstanding. The notes will be structurally subordinated to all future and existing obligations of our subsidiaries and will be effectively juniorto any secured debt we incur to the extent of the collateral securing such indebtedness. See “Risk Factors” beginning on page S-4 of this prospectus supplement and the section entitled “Risk Factors” in ourAnnual Report on Form 10-K for the year ended December31, 2024, which is incorporated by reference into thisprospectus supplement, for a discussion of certain risks that you should consider in connection with an investment inthe notes. Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of thesesecurities or passed upon the adequacy or accuracy of this prospectus supplement and the accompanying prospectus. Any representation to thecontrary is a criminal offense. (1)Plus accrued interest from December 11, 2025 if settlement occurs after that date. The underwriters expect to deliver the notes to purchasers through the book-entry delivery system of The Depository Trust Company (“DTC”) and itsparticipants, including Euroclear Bank SA/NV, as operator of the Euroclear System (“Euroclear”) and Clearstream Banking S.A. (“Clearstream”) on orabout December 11, 2025. WellsFargoSecurities DeutscheBankSecuritiesMorganStanleyUS Bancorp BarclaysGoldmanSachs&Co.LLCM&T Securities J.P.MorganSiebertWilliamsShank Table of Contents TABLE OF CONTENTS Prospectus Supplement ABOUT THIS PROSPECTUS SUPPLEMENTFORWARD-LOOKING STATEMENTSPROSPECTUS SUPPLEMENT SUMMARYRISK FACTORSUSE OF PROCEEDSCAPITALIZATIONDESCRIPTION OF NOTESU.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERSCERTAIN ERISA AND BENEFIT PLAN CONSIDERATIONSUNDERWRITING (CONFLICTS OF INTEREST)VALIDITY OF NOTESEXPERTSWHERE YOU CAN FIND MORE INFORMATION Prospectus ABOUT THIS PROSPECTUSRISK FACTORSFORWARD-LOOKING STATEMENTS.WHERE YOU CAN FIND MORE INFORMATIONTHE COMPANY.USE OF PROCEEDSDESCRIPTION OF THE DEBT SECURITIESDESCRIPTION OF COMMON STOCK.DESCRIPTION OF PREFERRED STOCK DESCRIPTION OF DEPOSITARY SHARES DESCRIPTION OF WARRANTS DESCRIPTION OF SUBSCRIPTION RIGHTS DESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE UNITS PLAN OF DISTRIBUTION VALIDITY OF SECURITIES EXPERTS We and the underwriters have not authorized anyone to provide you with information other than that contained or incorporated byreference in this prospectus supplement, the accompanying prospectus or any free-writing prospectus filed by us with the SEC. This prospectussupplement and the accompanying prospectus is an offer to sell only the notes offered hereby, and only under circumstances and injurisdictions where it is lawful to do so. You should not assume that the information contained or incorporated by reference in this prospectussupplement, the accompanying prospectus or any free-writing prospectus filed by us with the SEC is accurate as of any date other than the dateof the applicable document. Our businesses, financial condition, results of operations, liquidity, cash flows and prospects might have changedsince those dates. We expect that delivery of the notes will be made to investors on or about December 11, 2025, which will be the third business dayfollowing the date of this prospectus supplement (such settlement being referred to as “T+3”). Under Rule 15c6-1 under the SecuritiesExchange Act of 1934, as amended Table of Contents (the “Exchange Act”), trades in the secondary market are required to settle in one business day, unless the parties to any such trade expresslyagree otherwise. Accordingly, purchasers who wish to trade notes more than one business day prior to the deli