Its source is in the Orne department
It crosses the west of the Sarthe department from north to south.
It stretches for nearly 314 km
In the north of the Sarthe department, and more particularly in the Alpes Mancelles, the harshness of the Armorican massif forces the river to carve out a steep, winding valley, whereas from Fresnay-sur-Sarthe onwards, it finds the plain and looser soil, allowing it to flow slowly all the way to Le Mans. It continues as far south as Sablé-sur-Sarthe, where it joins the Mayenne to form the Maine.
Although the Sarthe was used for transport throughout the Middle Ages, only the downstream section from Le Mans was made navigable for large barges in the mid-19th century. The upstream section remains wild and unspoilt, ideal for a wide range of activities.