Ain River, river, eastern France, flowing 124 miles (200 km) southward from the Jura Plateau through Jura and Ain départements. The river emerges from its gorge near Pont-d’Ain, having powered several hydroelectric stations (the largest of which is the Barrage de Vouglans). The Ain then crosses the Dombes lowlands and joins the Rhône River. The river’s principal affluents include the Bienne and Albarine.