Saint-Vincent-sur-OustSaint-Vincent-sur-Oust is a commune in the Morbihan department of Brittany in north-western France.WWW saint-vincent-sur-oust.frGeographyThe river Oust forms all of the commune's northern and eastern borders; the river Arz forms most of its south-western border.DemographicsInhabitants of Saint-Vincent-sur-Oust are called in French Vincentais.