Saint-Denis-sur-Sarthon () is a commune in the Orne department in north-western France.
Notable Residents Saint Azélie-Marie ("Zélie") Guérin Martin mother of Saint Thérése of Liseux ( Saint Thérèse of the Child Jesus and the Holy Face)
The commune along with 26 others contains part of the Forêt d'ÃÂcouves.
The Commune along with another 11 communes shares part of a 5,255 hectare, Natura 2000 conservation area, called the Vallée du Sarthon et affluents.