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.

Thonon-les-Bains is part of a transborder metropolitan area known as Grand Genève.

Thonon-les-Bains was the historic capital of Chablais, a province of the old Duchy of Savoy.

A petition circulated in this part of the country (Chablais, Faucigny, Northern Genevois), but it collected no more than 13,600 signatures.

Thonon-les-Bains station has rail connections to Lyon, Évian-les-Bains, Annemasse and Geneva.