Sisteron. Sisteron a commune in southeastern France, in the Alpes-de-Haute-Provence département in the Provence-Alpes-Côte d'Azur region. The inhabitants are called the 'Sisteronnais'. Sisteron is situated on the banks of the River Durance just after the confluences of the rivers Buëch and Sasse. It is sometimes called the 'Porte de la Provence' (The Gateway to Provence) because it is in a narrow gap between two long mountain ridges (Baume/Gache and the Lure mountain/Moulard).