Mount's Bay is a bay on the English Channel coast of Cornwall, England, stretching from the Lizard Point to Gwennap Head. In the north of the bay, near Marazion, is St Michael's Mount; the origin of name of the bay. In summer, it is a generally benign natural harbour. However, in winter, onshore gales present maritime risks, particularly for sailing ships. There are more than 150 known wrecks from the nineteenth century in the area. The eastern side of the bay centred around Marazion and St Michael's Mount was designated as a Marine Conservation Zone in January 2016.

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.