Company: BCDRF
Filing Date: 2025-10-31
Form Type: 424B5
Source: 0001193125-25-260533
Chunk: 344

Company: Banco Santander, S.A.
Filing Date: 2025-10-31
Form: 424B5
Chunk 344
---
 | our exposure to operational losses (e.g., failed internal or external processes, people and systems); |

| • |     | changes in our ability to recruit, retain and develop appropriate senior management and skilled personnel; |

| • |     | the occurrence of force majeure, such as natural disasters, epidemics and pandemics, including the covid-19 pandemic, that impact our operations or impair the asset quality of our loan portfolio; |

| • |     | the impact of changes in the composition of our balance sheet on future interest income / (charges); and |

| • |     | potential losses associated with cyberattacks. |

Other factors could also adversely affect our results or the accuracy of forward-looking statements in this prospectus, and you should not consider the factors discussed here or in the Group’s 2022 Annual Report or any 173

of its interim reports filed on Form 6-K incorporated by reference herein, to be a complete set of all potential risks or uncertainties.

The forward-looking statements made in this prospectus speak only as of the date of this prospectus. We do not intend to publicly update or
revise these forward-looking statements to reflect events or circumstances after the date of this prospectus, and we do not assume any responsibility to do so. You should, however, consult any further disclosures of a forward-looking nature we made
in other documents filed with the SEC that are incorporated by reference into this prospectus.

174

$2,800,000,000 Banco Santander, S.A. $300,000,000 Senior Non Preferred Floating Rate Notes due 2030 $1,250,000,000 4.551% Senior Non Preferred Fixed Rate Notes due 2030 $1,250,000,000 5.127% Senior Non Preferred Fixed Rate Notes due 2035 PROSPECTUS SUPPLEMENT (to prospectus dated May 16, 2023) Joint Bookrunners

| Barclays |     | BofA Securities |     | Jefferies |     | J.P. Morgan |

| Mizuho |     | Santander |     | UBS Investment Bank |

Senior Co-Leads

| BMO |     | Scotiabank |     | Standard Chartered Bank AG |     | TD Securities |

Co-Leads

| Banco Sabadell |     | BB Securities Ltd |     | Blaylock Van, LLC |     | Rabo Securities |     | R. Seelaus & Co., LLC |

October 30,