The Lez (French pronunciation: [lɛz]; Occitan: Les) is a 29.6-kilometre (18.4 mi) river in the Hérault department in southern France. It is the main river of the city of Montpellier. The river has its source in the forest 5 km north of Saint-Clément-de-Rivière and it flows into the Mediterranean Sea at Palavas-les-Flots after first passing between two large lagoons and intersecting with the Canal du Rhône à Sète. Its longest tributary is the Mosson. The small fish Cottus petiti is endemic to a short stretch of the Lez.