Company: BCDRF
Filing Date: 2025-10-31
Form Type: 424B5
Source: 0001193125-25-260533
Chunk: 7

Company: Banco Santander, S.A.
Filing Date: 2025-10-31
Form: 424B5
Chunk 7
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 the Notes and neither Banco Santander nor the Underwriters are soliciting an offer to buy the Notes in any jurisdiction where the offer or sale is not permitted or where the person making the offer or sale is not qualified to do so or from any person to whom it is not permitted to make such offer or sale. We refer you to the information under“Underwriting (Conflicts of Interest)”in this prospectus supplement. You should assume that the information contained in this prospectus supplement, the accompanying prospectus and the information incorporated by reference into this prospectus supplement is accurate only as of their respective dates.

S-iii

ABOUT THIS PROSPECTUS SUPPLEMENT In this prospectus supplement, we use the following terms:

| • |     | “we,” “our” and “us” or “Banco Santander” means Banco Santander, 
 S.A.;                                                            |

| • |     | “Group” means Banco Santander, S.A. and its consolidated subsidiaries; |

| • |     | “dollars” and “$” refer to the currency of the United States; |

| • |     | “euro” and “€” refer to the currency of the Member States of the European Union                                                 
 (“EU”) that have adopted the single currency in accordance with the treaty establishing the European Community, as amended; and |

| • |     | “SEC” refers to the U.S. Securities and Exchange Commission. |

This document is not a prospectus for the purposes of Regulation (EU) No. 2017/1129 of the European Parliament and of the Council of 14 June 2017 on the prospectus to be published when securities are offered to the public or admitted to trading on a regulated market, and repealing Directive 2003/71/EC (the “Prospectus Regulation”). This document has been prepared on the basis that all offers of the Notes offered hereby made to persons in the European Economic Area (“EEA”) or in the United Kingdom (“UK”) will be made pursuant to an exemption under the Prospectus Regulation from the requirement to produce a prospectus in connection with offers of such Notes. The communication of this document and any other document or materials relating to the issue of the Notes offered hereby is not being made, and such documents and/or materials have not been approved, by an authorized person for the purposes of section 21 of the UK’s Financial Services and Markets Act 2000, as amended (“FSMA”). Accordingly, such documents and/or materials