Company: BCDRF
Filing Date: 2025-06-24
Form Type: 6-K
Source: 0000950103-25-007723
Chunk: 0

Company: Banco Santander, S.A.
Filing Date: 2025-06-24
Form: 6-K
Chunk 0
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<div align='center'>FORM 6-K

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Report of Foreign Issuer

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

For the month of June, 2025

Commission File Number: 001-12518

Banco Santander, S.A.

(Exact name of registrant as specified in its charter)

Ciudad Grupo Santander

28660 Boadilla del Monte (Madrid) Spain

(Address of principal executive office)</div>

Indicate by check mark whether the registrant files or will file annual
reports under cover of Form 20-F or Form 40-F:

| Form 20-F | X |     | Form 
 40-  |

<div align='center'>Banco Santander, S.A.

TABLE OF CONTENTS</div>

Item 1

Banco Santander, S.A., ("Santander"
or the "Offeror") in accordance with the provisions of the securities market legislation, communicates the following:

<div align='center'>INSIDE INFORMATION</div>

Santander announces that it is inviting
holders (subject to the offer restrictions and the other information under Important Information set forth below) of its outstanding €1,500,000,000
4.375 per cent. Non-Step-Up Non-Cumulative Contingent Convertible Perpetual Preferred Tier 1 Securities (ISIN: XS2102912966) (the "Preferred Securities") to tender their Preferred Securities for purchase by the Offeror for cash in an aggregate nominal amount of up to
the Maximum Acceptance Amount (as defined below), subject to pro rata scaling, if applicable, and subject to applicable law and
regulation and the offer and distribution restrictions and the satisfaction or waiver of the New Financing Condition (as defined below)
and the other conditions described in the tender offer memorandum dated 24 June 2025 (the "Tender Offer Memorandum")
(the "Offer"). The repurchase of the Preferred Securities has been authorised by the European Central Bank.

| Description of Preferred Securities                                                                                    | ISIN         | Outstanding Nominal Amount | First Optional Redemption Date | Purchase Price | Amount subject to the Offer                                                                                                                                                                                                                                                                                                                                                                                                             |
| €1,500,000,000 4.375 per cent. Non-Step-Up Non-Cumulative Contingent Convertible Perpetual Preferred Tier