Company: SNY
Filing Date: 2025-10-27
Form Type: 424B5
Source: 0001193125-25-250786
Chunk: 74

Company: Sanofi
Filing Date: 2025-10-27
Form: 424B5
Chunk 74
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 incorporated by reference at no cost, by contacting us orally or in writing at the following address and telephone number: Investor Relations, 46, avenue de la Grande Armée, 75017 Paris, France, Tel. No.: +33-1-53-77-40-00. The 2023 Form 20-Fand any other information incorporated by reference is considered to be a part of this prospectus. The information in this prospectus, to the extent applicable, automatically updates and supersedes the information in the 2023 Form 20-F. 3

You should rely only on the information that we incorporate by reference or provide in this
prospectus or any applicable prospectus supplement(s). We have not authorized anyone to provide you with different information. We are not making an offer of these debt securities in any jurisdiction where the offer is not permitted. You should not
assume that the information in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front of those documents.

4

ENFORCEABILITY OF CERTAIN CIVIL LIABILITIES We are a limited liability company ( société anonyme) organized under the laws of France, and most of our officers and directors reside outside the United States. In addition, a substantial portion of our assets is located outside of the United States. As a result, it may be difficult for investors:

| • |     | to obtain jurisdiction over us or our non-U.S. resident officers and                                                                                                                                                                                   
 directors in U.S. courts, or obtain evidence in France or from any French citizen or any individual being resident in France or any officer, representative, agent or employee of a legal person having its registered office or an establishment in a 
 territory of France, in connection with actions predicated on the civil liability provisions of the U.S. federal securities laws;                                                                                                                      |

| • |     | to enforce in U.S. courts judgments obtained in such actions against us or our 
 non-U.S. resident officers and directors;                                      |

| • |     | to bring an original action in a French court to enforce liabilities based upon the U.S. federal securities laws 
 against us or our non-U.S. resident officers or directors; and                                                   |

| • |     | to enforce against us or our directors in non-U.S. courts, including                                                        
 French courts, judgments of U.S. courts predicated upon the civil liability provisions of the U.S. federal securities laws. |

Nevertheless, a final judgment for the