St Michael's Mount is a tidal island in Mount's Bay, Cornwall, England, United Kingdom. The island is a civil parish and is linked to the town of Marazion by a causeway of granite setts, passable between mid-tide and low water. It is managed by the National Trust, and the castle and chapel have been the home of the St Aubyn family since around 1650.

A tidal island is a raised area of land within a waterbody, which is connected to the larger mainland by a natural isthmus or man-made causeway that is exposed at low tide and submerged at high tide, causing the land to switch between being a promontory/peninsula and an island depending on tidal conditions.