The Susa Valley (Italian: Val di Susa, French: Val de Suse) is a valley in the Piedmont region of northern Italy, located between the Graian Alps in the north and the Cottian Alps in the south. It is the longest valley in Italy. It extends over 50 km (31 mi) in an east-west direction from the French border to the outskirts of Turin. The valley takes its name from the city of Susa which lies in the valley. The Dora Riparia river, a tributary of the Po, flows through the valley.
A motorway runs through the valley from Turin to Chambéry in France, over the Col du Mont Cenis or by the Fréjus tunnel, and to Briançon, also in France, over the Col du Mont-Genèvre.