Menthonnex-en-Bornes (Savoyard: Mintné-an-Beûrne) is a commune in the Haute-Savoie department in the Auvergne-Rhône-Alpes region in south-eastern France.
Menthonnex-en-Bornes is located as the crow flies to the north of the departmental seat, the commune of Annecy.
By road, the commune is about halfway between Geneva () and Annecy () on the plateau of Bornes. It is separated from the mountain Salève by the river valley, which forms its western border. The southern border is defined by the stream Grand Verray.
The final ex in Menthonnex is not pronounced; it should be read as Menthonné.