The Gave de Pau starts in the Cirque de Gavarnie, in the "Parc national des Pyrénées" ("Pyrénées National Park"), in the "commune" of Gavarnie, Hautes-Pyrénées department, at an altitude of about . The upper part of the river is known as "Gave de Gavarnie"; the name "Gave de Pau" is given to the river after the Gave de Gavarnie joins the Bastan river at Luz-Saint-Sauveur.