Mont-Saint-Michel is a tidal island and mainland commune in Normandy, France. The island lies approximately one kilometre off France's nort…Mont-Saint-Michel is a tidal island and mainland commune in Normandy, France. The island lies approximately one kilometre off France's north-western coast, at the mouth of the Couesnon River near Avranches and is 7 hectares in area. The mainland part of the commune is 393 hectares in area so that the total surface of the commune is 400 hectares. As of 2019, the island had a population of 29.