The Hermance is a river that rises in France in Haute-Savoie, between Machilly and Loisin, and flows for 7 kilometres through the small valley from Hermance and the commune of Veigy-Foncenex where it marks the Swiss-French border on the last 6 kilometres of its course by bordering the communes of Anières and Hermance in Switzerland and Chens-sur-Léman in France, before flowing into Lake Geneva.