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 April, 2026

 

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)

 

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
 
 

 

   

Banco Santander,
S.A.

 

TABLE OF CONTENTS

 

Item 

 

 
 

1
Report of Other Relevant Information dated April 16, 2026

 

 

 

 

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

 

OTHER RELEVANT INFORMATION

 

Reference is made
to our notice of inside information of 4 February 2026 (official registry number 3077) (the “Buyback Commencement Communication”),
relating to the buyback programme of own shares (the “Buyback Programme”) approved by the Board of Directors of Banco
Santander.

 

Pursuant to article 5 of Regulation (EU) no. 596/2014
on Market Abuse of 16 April 2014, and articles 2.2 and 2.3 of Commission Delegated Regulation (EU) 2016/1052, of 8 March 2016, the Bank
informs of the transactions carried out over its own shares between 8 and 15 April (both inclusive).

 

The cash amount of the shares purchased to 15 April
2026 as a result of the execution of the Buyback Programme amounts to 2,705,497,424 Euros, which represents approximately 53.8% of the
maximum investment amount of the Buyback Programme. The programme was announced together with its other characteristics through the Buyback
Commencement Communication. With these purchases, the Bank has repurchased approximately 16.8% of its outstanding shares as of 2021.

 

Date
Security
Transaction
Trading venue
Number of shares
Weighted average price (€)

08/04/2026
SAN
Purchase
XMAD
1,000
10.4867

09/04/2026
SAN
Purchase
XMAD
1,000
10.3363

10/04/2026
SAN
Purchase
XMAD
1,000
10.4871

13/04/2026
SAN
Purchase
XMAD
1,000
10.3315

14/04/2026
SAN
Purchase
XMAD
1,000
10.5769

15/04/2026
SAN
Purchase
XMAD
1,000
10.6303

 
 
 
TOTAL
6,000
 

 

Issuer name: Banco Santander, S.A. – LEI
5493006QMFDDMYWIAM13

 

Reference of the financial instrument: ordinary
shares – Code ISIN ES0113900J37

 

Detailed information of the transactions carried
out within the referred period is attached as Annex I.

 

Boadilla del Monte (Madrid), 16 April 2026

 

 

  

 

ANNEX I

 

Detailed
information on each of the transactions carried out within the context of the Buy-back Programme between 08/04/2026 and 15/04/2026 (both
inclusive)

 

(https://www.santander.com/content/dam/santander-com/es/documentos/cumplimiento/do-anexo-i-8-a-15-abril-2026-es.pdf)

 

 

 

SIGNATURE

 

Pursuant to the
requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned,
thereunto duly authorized.

 

 
Banco Santander, S.A.

 
 

 
 

Date:
April 16, 2026
By:
/s/ Pedro de Mingo Kaminouchi

 
 
 
Name:
Pedro de Mingo Kaminouchi

 
 
 
Title:
Head of Corporate Compliance