A tidal island is a piece of land that is connected to the mainland by a natural or man-made causeway that is exposed at low tide and submerged at high tide. Because of the mystique surrounding tidal islands, many of them have been sites of religious worship, such as Mont Saint-Michel with its Benedictine Abbey. Tidal islands are also commonly the sites of fortresses because of their natural fortifications.

Le Mont-Saint-Michel is an island and mainland commune in Normandy, France.

The island is located about one kilometer (0.6 miles) off the country's northwestern coast, at the mouth of the Couesnon River near Avranches and is 7 hectares (17 acres) in area.

The tides can vary greatly, at roughly 14 metres (46 ft) between highest and lowest watermarks. Popularly nicknamed "St. Michael in peril of the sea" by medieval pilgrims making their way across the flats, the mount can still pose dangers for visitors who avoid the causeway and attempt the hazardous walk across the sands from the neighbouring coast.

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