Located on the right bank of the Rance estuary in the north of the Ille-et-Villaine department, the territory of the commune of Saint-Suliac forms a sort of peninsula bordered by the Goutte stream (photo). Subject to the tides, the estuary of the stream constitutes a salt marsh rich in phragmitaias (Phragmites australis) with a dense stand. The Goutte stream is one of the classified sites of the Rance estuary considered as a Natura 2000 site of Community importance.