The Adour (, ) is a river in southwestern France. It rises in High-Bigorre (Pyrenees), at the Col du Tourmalet, and flows into the Atlantic Ocean (Bay of Biscay) near Bayonne. It is long, of which the uppermost as the Adour du Tourmalet. At its final stretch, i.e. on its way through Bayonne and a short extent upstream, the river draws the borderline between the Northern Basque Country and Landes regions.