Mont Saint-Michel (English: Mount Saint Michael) is a rocky tidal island in Normandy, roughly one kilometre from the north coast of France at the mouth of the Couesnon River near Avranches.
The inhabitants of Mont-Saint-Michel are called the Montois.
In prehistoric times the bay was land, as sea levels rose erosion shaped the coastal landscape over millions of years. Several blocks of granite or granulite emerged in the bay, having resisted the wear and tear of the ocean better than the surrounding rocks. These included Lillemer, the Mont-Dol, Tombelaine and Mont Tombe, later called Mont Saint-Michel.
Mont Saint-Michel was previously connected to the mainland via a thin natural land bridge, which before modernization was covered at high tide and revealed at low tide. Thus, Mont Saint Michel gained a mystical quality, being an island half the time and being attached to land the other: a tidal island.
However, the insular character of the mount has been compromised by several developments. Over the centuries, the coastal flats have been polderised to create pasture. The south coast of Mont-Saint-Michel has thus become farther to the shore and the mount. The Couesnon River has been canalised, reducing the flow of water and thereby encouraging a silting-up of the bay. In 1879, the land bridge was fortified into a true causeway. This prevented the tide from scouring the silt round the mount. There are currently plans to remove the causeway and replace it with a bridge and a shuttle.
On 16 June 2006, the Prime Minister of France, Dominique de Villepin, announced a €150 million project (Projet Mont Saint-Michel) to build a hydraulic dam that will help remove the accumulated silt and make Mont Saint-Michel an island again. It is expected to be completed by 2012.