Company: BCDRF
Filing Date: 2025-04-30
Form Type: 6-K
Source: 0000891478-25-000078
Chunk: 0

Company: Banco Santander, S.A.
Filing Date: 2025-04-30
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 April, 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.
#### ________________________

### TABLE OF CONTENTS
| Item 1. January - March 2025 Financial Report |     | 3 |

| January - March |     | 2025 |

Index

| 3  |     | KEY CONSOLIDATED DATA                               |
| 5  |     | BUSINESS MODEL                                      |
| 6  |     | GROUP FINANCIAL INFORMATION                         |
| 6  |     | General background                                  |
| 7  |     | Highlights of the period                            |
| 9  |     | Income statement                                    |
| 16 |     | Balance sheet                                       |
| 19 |     | Solvency ratios                                     |
| 20 |     | Risk management                                     |
| 24 |     | The Santander share                                 |
| 26 |     | FINANCIAL INFORMATION BY SEGMENT                    |
| 44 |     | SUSTAINABILITY                                      |
| 45 |     | CORPORATE GOVERNANCE                                |
| 46 |     | APPENDIX                                            |
| 47 |     | Financial information                               |
| 74 |     | Alternativeperformancemeasures                      |
| 86 |     | Interim condensed consolidated financial statements |
| 89 |     | Glossary                                            |
| 90 |     | Important information                               |

This report was approved by the board of directors on 29 April 2025, following a favourable report from the audit committee. Important information regarding this report can be found on pages 90 and 91.

| Key consolidated data