桑坦德银行美股招股说明书(2026-04-08版)

$ Banco Santander, S.A. $Senior Non Preferred Floating Rate Notes due 2029$% Senior Non Preferred Fixed Rate Notes due 2029$% Senior Non Preferred Fixed Rate Notes due 2031$% Senior Non Preferred Fixed Rate Notes due 2036 We are offering $principal amount of Senior Non Preferred Floating Rate Notes due 2029 (the “2029 FloatingRate Notes”), $principal amount of% Senior Non Preferred Fixed Rate Notes due 2029 (the “2029 FixedRate Notes”), $principal amount of% Senior Non Preferred Fixed Rate Notes due 2031 (the “2031 FixedRate Notes”), and $principal amount of% Senior Non Preferred Fixed Rate Notes due 2036 (the “2036 FixedRate Notes” and, together with the 2029 Floating Rate Notes, the 2029 Fixed Rate Notes and the 2031 Fixed Rate Notes, the“Notes”). The 2029 Floating Rate Notes will bear interest at the 2029 Floating Rate Interest Rate (as defined herein). From andincluding the date of issuance, interest will be payable quarterly in arrears on the 2029 Floating Rate Notes onJanuary, April, Julyand Octoberof each year, beginning on July, 2026. Unlesswe redeem the 2029 Floating Rate Notes earlier, the 2029 Floating Rate Notes will be due on April, 2029. The 2029 Fixed Rate Notes will bear interest at a rate of% per year. From and including the date of issuance,interest will be payable semi-annually in arrears on the 2029 Fixed Rate Notes on Apriland Octoberof eachyear, beginning on October, 2026. Unless we redeem the 2029 Fixed Rate Notes earlier, the 2029 Fixed Rate Noteswill be due on April, 2029. The 2031 Fixed Rate Notes will bear interest at a rate of% per year. From and including the date of issuance,interest will be payable semi-annually in arrears on the 2031 Fixed Rate Notes on Apriland Octoberof eachyear, beginning on October, 2026. Unless we redeem the 2031 Fixed Rate Notes earlier, the 2031 Fixed Rate Noteswill be due on April, 2031. The 2036 Fixed Rate Notes will bear interest at a rate of% per year. From and including the date of issuance,interest will be payable semi-annually in arrears on the 2036 Fixed Rate Notes on Apriland Octoberof eachyear, beginning on October, 2026. Unless we redeem the 2036 Fixed Rate Notes earlier, the 2036 Fixed Rate Noteswill be due on April, 2036. The Notes will be issued in minimum denominations of $200,000 and integral multiples of $200,000 in excess thereof. The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and theaccompanying prospectus are not an offer to sell these securities nor do they seek an offer to buy these securities in any jurisdiction where the offer orsale is not permitted.The payment obligations of Banco Santander, S.A. (“Banco Santander”) in respect of principal under the Notes constitutedirect, unconditional, unsubordinated and unsecured senior non preferred obligations (créditos ordinarios no preferentes) ofBanco Santander and, in accordance with Additional Provision 14.2 of Law 11/2015 (as defined herein) (but subject to any otherranking that may apply as a result of any mandatory provision of law (or otherwise)), upon the insolvency of Banco Santander,such payment obligations rank (i)pari passuamong themselves and with any other Senior Non Preferred Liabilities (as definedherein), (ii) junior to the Senior Higher Priority Liabilities (as defined herein) (and, accordingly, upon the insolvency of BancoSantander, Table of Contents the payment obligations of Banco Santander in respect of principal under the Notes will be met after payment in full of the Senior Higher PriorityLiabilities) and (iii)senior to any present and future subordinated obligations (créditos subordinados) of Banco Santander in accordance withArticle281 of the Spanish Insolvency Law (as defined herein). By its acquisition of the Notes, each holder (which, for the purposes of this clause, includes each holder of a beneficial interest in theNotes) acknowledges, accepts, consents to and agrees to be bound by the terms of the Notes related to the exercise of the Bail-in Power (asdefined herein) set forth under“Description of Debt Securities—Agreement and Acknowledgement with Respect to the Exercise of the Bail-inPower” in the accompanying prospectus. See“Notice to Investors”on page S-i of this prospectus supplement for further information. The Notes are not deposits or savings accounts and are not insured by the Federal Deposit Insurance Corporation or any other governmentalagency of the Kingdom of Spain, the United States or any other jurisdiction. Subject to the terms and conditions under “Description of the Notes—Redemption and Repurchase,” we may redeem the Notes of any series, inwhole but not in part, at 100% of their principal amount plus accrued and unpaid interest (if any), (i) at any time upon the occurrence of a Tax Event (asdefined herein), (ii) at any time upon the occurrence of a TLAC/MREL Disqualification Event (as defined herein) or (iii)if 75% or more of the initialagg