The Sarthe (French pronunciation: [saʁt]) is a 313.9-kilometre-long (195.0 mi) river in western France. Together with the river Mayenne it forms the river Maine, which is a tributary to the river Loire.Its source is in the Orne department, near Moulins-la-Marche. It flows generally southwest, through the following departments and towns:Orne: Le Mêle-sur-Sarthe, AlençonSarthe: Fresnay-sur-Sarthe, Beaumont-sur-Sarthe, Le Mans, Sablé-sur-SartheMaine-et-Loire: Châteauneuf-sur-Sarthe, Tiercé, AngersIts two main tributaries are the Loir and the Huisne.