The Doubs is a French and Swiss river, a sub-tributary of the Rhône through the Saône. It gave its name to the French department of Doubs. With a total length of 453 km, of which 430 km are on French territory. It is the tenth French river by its length and the fourth river after the Marne, the Lot and the Saône. It has its source in the French commune of Mouthe at an altitude of 945.5 m, and flows first mainly to the northeast, watering the towns of Pontarlier and Morteau in particular, then to the southwest, crossing the town of Besançon after having served as a border between France and Switzerland. Then an incursion into Swiss territory and through the Pays de Montbéliard. It flows into the Saône at Verdun-sur-le-Doubs.