Aux Sources de la Sèvre is a 300 km BRM road cycling brevet starting in Saint-Herblain, west of Nantes. Riders check in early at the Union Sportive St Herblain club base on Rue de Charente. They must complete a challenging 303 km route with approximately 2,950 m of elevation gain by the night finish. As part of the Brevets Randonneurs Mondiaux system, the focus is on long-distance randonneuring: completing the route independently, managing personal stops, and achieving the necessary controls within the time limit.
The route traces the narrative suggested by its name, leading from the mouth of the Sèvre Nantaise, where it joins the Loire in Nantes, towards the river's origins on the Gâtines plateau, near the border of Deux-Sèvres and Vendée. This is a fully self-supported ride, suitable for experienced road cyclists and randonneurs adept at planning their own food, water, lights, clothing, and pacing for an extended day. The entry fee is modest, juniors participate without charge, and the organizer offers a hot meal at the finish, contributing to the event's club-brevet atmosphere over a commercial sportive feel.