Darnius is part of the region of Empordà, province of Girona. The municipal area has an extension of 35 km² and 193 m altitude.
The limits of the municipal term are to the north with Agullana, to the east with Biure, to the south with Boadella d’Empordà and to the west with Maçanet de Cabrenys. It includes the neighborhoods of El Barri del Pantà, the Neighborhood of Amunt, l’Arnera, Ricardell and the Neighborhood of Mont-roig.
Much of the area of Darnius is located in the Muga river basin and bathed by three other rivers: The Ricardell, the Llobregat d’Empordà and the Arnera, which joins the Muga and form the Darnius reservoir- Boadella, where swimming is allowed, and various nautical activities can be practiced.