Company: BCDRF
Filing Date: 2025-02-28
Form Type: 6-K
Source: 0000891478-25-000051
Chunk: 0

Company: Banco Santander, S.A.
Filing Date: 2025-02-28
Form: 6-K
Chunk 0
---
#### 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 February, 2025

#### Commission File Number: 001-12518

#### Banco Santander, S.A.
<div align='center'>(Exact name of registrant as specified in its charter)</div>

#### Ciudad Grupo Santander

#### 28660 Boadilla del Monte (Madrid) Spain
<div align='center'>(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 ☒ Form 40-F ☐</div>

#### BANCO SANTANDER, S.A.
#### ________________________

### EXHIBIT INDEX
| EXHIBIT NUMBER |     | DESCRIPTION       |
| 99.1           |     | 2024Annual Report |

### 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:    28 February 2025 |     | By:                   |     | /s/ José García Cantera |
|                           |     | Name:                 |     | José García Cantera     |
|                           |     | Title:                |     | Chief Financial Officer |