Mont-Saint-Michel, rocky islet and famous sanctuary in Manche  département, Normandy région, France, off the coast of Normandy. It lies 41 miles (66 km) north of Rennes and 32 miles (52 km) east of Saint-Malo. Around its base are medieval walls and towers above which rise the clustered buildings of the village with the ancient abbey crowning the mount. One of the more popular tourist attractions in France, Mont-Saint-Michel was designated a UNESCO World Heritage site in 1979.

Mont-Saint-Michel is almost circular (about 3,000 feet [900 metres] in circumference) and consists of a granite outcrop rising sharply (to 256 feet [78 metres]) out of Mont-Saint-Michel Bay (between Brittany and Normandy). Most of the time it is surrounded by vast sandbanks and becomes an island only when the tides are very high. Before the construction of the 3,000-foot causeway that connects the island to land, it was particularly difficult to reach because of quicksand and very fast-rising tides. The causeway, however, has become a barrier to the removal of material by the tides, resulting in higher sandbanks between the islet and the coast.