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 30 July 2025 (official registry number 2844) (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 11 and 17 September 2025 (both inclusive).

The cash amount of the shares purchased to 17 September 2025 as a result of the execution of the Buyback Programme amounts to 424,880,214 Euros, which represents approximately 25% 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 14.5% of its outstanding shares as of 2021.

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), 18 September 2025

ANNEX I

Detailed information on each of the transactions carried out within the context of the Buy-back Programme between 11/09/2025 and 17/09/2025 (both inclusive)