Company: BCDRF
Filing Date: 2025-06-03
Form Type: 6-K
Source: 0000950103-25-006866
Chunk: 0

Company: Banco Santander, S.A.
Filing Date: 2025-06-03
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-F |

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

TABLE OF CONTENTS</div>

Item 1

Banco Santander, S.A. (the “Bank”
or “Banco Santander”), in compliance with the securities market legislation, hereby communicates the following:

Banco Santander share capital reduces by 1.76% following completion of buy-back programme.

Reference is made to our notice of inside
information of 5 February 2025 (official registry number 2584) (the “Buy-back Commencement Communication”), relating
to the buyback programme of own shares approved by the board of directors of Banco Santander (the “Buy-back Programme”
or the “Programme”). The Bank informs that, after the last acquisitions mentioned below, the maximum investment
provided for in the Buy-back Programme (i.e. EUR 1,587 million) has been reached, having acquired a total of 267,166,950 own shares, representing
approximately 1.76% of the Bank’s share capital. The acquisition of shares under the Buy-back Programme has been communicated on
a regular basis, pursuant to the provisions of Articles 2.2 and 2.3 of the Commission Delegated Regulation (EU) No. 2016/1052. As
a consequence of the above, the Buy-back Programme has been terminated in accordance with the terms set out when it was announced.

As disclosed in the Buy-back Commencement Communication, the purpose
of the Programme was to reduce the Bank’s share capital by redeeming the shares acquired thereunder, which was authorised by the
European Central Bank on 31 January 202