Castelsarrasin
Castelsarrasin town hall
Administration
Country	France
Region	Midi-Pyrénées
Department	Tarn-et-Garonne
Arrondissement	Castelsarrasin
Canton	Castelsarrasin
Mayor	Jean-Philippe Bésiers (2014-2020)
Statistics
Elevation	61–97 m (200–318 ft) (avg. 84 m/276 ft)
Land area1	76.77 km2 (29.64 sq mi)
Population2	13,765  (2014)
- Density	179/km2 (460/sq mi)
INSEE/Postal code	82033/ 82100
Website	www.ville-castelsarrasin.fr
1 French Land Register data, which excludes lakes, ponds, glaciers > 1 km² (0.386 sq mi or 247 acres) and river estuaries.
2Population without double counting: residents of multiple communes (e.g., students and military personnel) only counted once.

Castelsarrasin (Occitan: Los Sarrasins) is a commune in the Tarn-et-Garonne department in the Occitanie region of France. It is the second city in Tarn-et-Garonne with more people living in it, after Montauban.

It is a subprefecture in the department and the capital of the Castelsarrasin arrondissement.