Thonon-les-Bains, 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.

Haute-Savoie is a department in the Auvergne-Rhône-Alpes region of Southeastern France, bordering both Switzerland and Italy. Its prefecture is Annecy. To the north is Lake Geneva; to the south and southeast are Mont Blanc and the Aravis mountain range.