The Hermance (French pronunciation: [ɛʁmɑ̃s]) is a river in France and Switzerland, that discharges into Lake Geneva. It rises near Loisin in Haute-Savoie, France, at 563 m elevation. In its lower half, downstream from Veigy, it marks the Swiss-French border. It flows into Lake Geneva between the villages Hermance (Switzerland) and Chens-sur-Léman (France), at 372 m elevation. Its total length is 14 km of which 6.5 kilometres on the border. Its catchment area is 42.5 km2, of which 37 km2 in France.
