The Arrats is a 162 km (101 mi) long river in southern France, left tributary of the Garonne. Its source is in the northern foothills of the Pyrenees, near Sariac-Magnoac. It flows north through the following départements and towns:

• Hautes-Pyrénées
• Gers: Castelnau-Barbarens, Aubiet, Mauvezin, Saint-Clar
• Tarn-et-Garonne: Saint-Loup

It flows into the Garonne near Valence, between Castelsarrasin and Agen.