Company: BCDRF
Filing Date: 2025-07-31
Form Type: 6-K
Source: 0000891478-25-000113
Chunk: 0

Company: Banco Santander, S.A.
Filing Date: 2025-07-31
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 July, 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
| Part 1                                              |     |     |
| Interim consolidated directors’ report              |     |   3 |
| Interim unaudited consolidated financial statements |     |  98 |
| Part 2                                              |     |     |
| Supplemental information                            |     | 161 |

| Part 1. Interim consolidated directors' report and interim unaudited consolidated financial statements |

| January - June |     | 2025 |

Index

| 3  |     | Interim consolidated directors' report              |
| 3  |     | SIGNIFICANT EVENTS IN THEPERIOD                     |
| 4  |     | KEY CONSOLIDATED DATA                               |
| 6  |     | BUSINESS MODEL                                      |
| 7  |     | GROUP FINANCIAL INFORMATION                         |
| 7  |     | General background                                  |
| 8  |     | Highlights of the period                            |
| 10 |     | Income statement                                    |
| 17 |     | Balance sheet                                       |
| 20 |     | Solvency ratios                                     |
| 21 |     | Risk management                                     |
| 25 |     | The Santander share                                 |
| 27 |     | FINANCIAL INFORMATION BY SEGMENT                    |
| 45 |     | SUSTAINABILITY                                      |
| 46 |     | CORPORATEGOVERNANCE                                 |
| 47 |     | APPENDIX                                            |
| 48 |     | Financial information