CASTELSARRASIN, a town of south-western France, cap ital of an arrondissement in the department of Tarn-et-Garonne, 12m. W. of Montauban. Pop. (1931), 2,984. The name appears in the 13th century. Castrum Cerrucium, Castel-sur-Azine (from the neighbouring stream, Azine) and Castellum Sarracenum are suggested derivations. The town is situated on the left bank of the lateral canal of the Garonne about a mile from the right bank of the river. Promenades occupy the site of the old fortifications. Its chief building is the 13th century brick church of St. Sauveur, typical of the Tolosan style.