The Isère is a French Alpine river that flows through the Savoie and Isère departments in southeastern France. It is a tributary of the Rhône River, and its source is located in the Vanoise Massif in the Graian Alps. The Isère is approximately 230 miles long and has a drainage basin of about 4, 000 square miles. It is an important source of hydroelectric power and is used for irrigation and drinking water.