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 27 September 2023 (official registry number 1979) (the "Buy-back Commencement Communication"), relating to the buyback programme of own shares (the "Buy-back 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, on the basis of the information received from Goldman Sachs International as intermediary in charge of executing the Buy-back Programme, of the transactions carried out over its own shares between 14 and 20 December 2023 (both inclusive).

The cash amount of the shares purchased to 20 December 2023 as a result of the execution of the Buy-back Programme amounts to 967,441,273 Euros, which represents approximately 74% of the maximum investment amount of the Buy-back Programme. The programme was announced together with its other characteristics through the Buy-back Commencement Communication.

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), 21 December 2023

ANNEX I

Detailed information on each of the transactions carried out within the context of the Buy-back Programme between 14/12/2023 and 20/12/2023 (both inclusive).