Company: SNY
Filing Date: 2025-10-27
Form Type: 424B5
Source: 0001193125-25-250786
Chunk: 7

Company: Sanofi
Filing Date: 2025-10-27
Form: 424B5
Chunk 7
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 20-F for the year ended December 31, 2024 filed with the SEC on February 13, 2025 (the “2024 Form 20-F”) (File 
 No. 001-31368);                                                                                                |

| • |     | Any document filed in the future with the SEC under Sections 13(a) and 13(c) or 15(d) of the Exchange Act after                                                                                                                                           
 the date of this prospectus supplement and the attached prospectus and until this offering is completed. Any report on Form 6-K that we furnish to the SEC on or after the date of this prospectus supplement (or                                         
 portions thereof) is incorporated by reference in this prospectus supplement and the attached prospectus only to the extent that the report expressly states that we incorporate it (or such portions) by reference in this prospectus supplement and the 
 attached prospectus and that it is not subsequently superseded.                                                                                                                                                                                           |

The consolidated financial statements contained in the 2024 Form 20-Fhave been prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the International Accounting Standards Board (IASB) and with IFRS as endorsed by the European Union, as of December 31, 2024. S-4

You may request a copy of documents incorporated by reference at no cost, by contacting us
by telephone or in writing at the following address and telephone number: Investor Relations, 46, avenue de la Grande Armée, 75017 Paris, France, email: investor.relations@sanofi.com; or the following telephone number: +33 1 53 77 40 00.

The 2024 Form 20-F and any other information incorporated by reference is considered to be a part of
this prospectus supplement and the attached prospectus. The information in this prospectus supplement, to the extent applicable, automatically updates and supersedes the information in the 2024 Form 20-F.

We have not, and the underwriters have not, authorized any other person to provide you with any information, other than the information contained or incorporated by reference in this prospectus supplement, the attached prospectus and any related free-writing prospectus we prepare or authorize, and we take no responsibility for any other information that others may give you. We are not, and the underwriters are not, making an offer to sell these notes in any jurisdiction where the offer or sale is not permitted. You should not assume that the information appearing in this