Thonon-les-Bains (French pronunciation: ​[tɔ.nɔ̃.lɛ.bɛ̃]; Arpitan: Tonon), often simply referred to as Thonon, is a subprefecture of the Haute-Savoie department in the Auvergne-Rhône-Alpes region in Eastern France. In 2018, the commune had a population of 35,241. Thonon-les-Bains is part of a transborder metropolitan area known as Grand Genève. It is situated on the shores of Lake Geneva (French: Lac Léman, or simply Le Léman).