The Arros (; ) is a right tributary of the Adour, in the Southwest of France. It is long.
The name Arros is based on the root Arr- 'stone' and the suffix -os.
The Arros rises in the Baronnies of Pyrenees, southeast of Bagnères-de-Bigorre, below the Signal de Bassia (1 921 m).
It flows north through a narrow valley defended by the castle of Mauvezin and the bastide of Tournay. It joins the Adour before it turn west, upstream from Riscle.