Fondation Dosne-Thiers, Historical research library in 9th arrondissement, Paris, France.

The Fondation Dosne-Thiers is a research library and museum in the 9th arrondissement housed in a protected historic mansion at Place Saint-Georges. The building contains books, manuscripts, prints, and drawings focusing on French history between 1789 and 1900.

The building was constructed in 1873 by architect Alfred-Philibert Aldrophe, replacing an earlier mansion destroyed during the Paris Commune. The foundation was later established to preserve personal collections for French historical research and make them accessible for scholarly purposes.

The name honours Adolphe Thiers, president of the Republic from 1871 to 1873, and his wife Élise Dosne, who lived here; the donor was Élise's sister Félicie Dosne. The ground-floor and first-floor salons are rented for study days, exhibitions, conferences and concerts, and have served as film and photo-shoot sets. Frédéric Masson's Napoleonic objects and paintings are regularly lent to exhibitions.

Guided tours of the mansion run year-round for groups, by appointment and with a lecturer; the building is otherwise open free of charge during the Journées du Patrimoine. The Bibliothèque Thiers receives researchers and students on Thursdays and Fridays from 12:00 to 18:00, and consulting manuscripts, prints or reserve books requires a recommendation from a member of the Institut de France. The entrance is at 27, place Saint-Georges in the 9th arrondissement.

Frédéric Masson, an academician and specialist in Napoleonic history, directed the mansion as a military hospital during the First World War. On his death he left the foundation 796 boxes of manuscripts, 1,000 drawings, 30,000 prints, 70,000 books and over 2,000 objects and paintings, mostly on the First Empire.