St Mary's Island may refer to:

Places

;England *

St Mary's Island, Kent St Mary's Island, is part of the Chatham Maritime development area in Medway, South East England. It is located at the northern end of Chatham, Medway, Chatham, adjacent to Brompton and Gillingham, Medway, Gillingham. Once part of the Chatham ...

, in Medway *

St Mary's Island, River Thames St Mary's Island is a tiny island in the River Thames in England. It has a size of about 150 m by 50 m. St Mary's Island (Tyne and Wear) St Mary's Island, sometimes referred to as Bait Island is a small sandstone island near the seaside resort of Whitley Bay, Tyne and Wear, England. It is a Local Nature Reserve. St Mary's Island was originally called Bates Island, Hartley Bate ...

, in the metropolitan county of Tyne and Wear *

St Mary's, Isles of Scilly St Mary's () is the largest and most populous island of the Isles of Scilly, an archipelago off the southwest coast of Cornwall in England, United Kingdom. Description St Mary's has an area of — 40 percent of the total land area of the Isles ...

, in the county of Cornwall ;India *

St. Mary's Islands St. Mary's Islands, also known as Thonsepar, are a set of four small islands in the Arabian Sea, off the coast of Malpe in Udupi, Karnataka, India. They are known for their distinctive geological formation of Columnar jointing, columnar rhyolit ...

, in the state of Karnataka ;Isle of Man *

St Mary's Isle St Mary's Isle (also known as Conister Rock or the Tower of Refuge, Manx: or ) is a partially submerged reef in Douglas Bay on the Isle of Man. Prior to 1832 the rock was the property of the Quane family until John Quane, Attorney General of ...

, Douglas Bay ;Madagascar *

Île Sainte-Marie Nosy Boraha , also known as Sainte-Marie, main town Ambodifotatra, is an island off the east coast of Madagascar. The island forms an administrative district within Analanjirofo Region, and covers an area of 222 km2. It has a population e ...

, also known as St Mary's Island in English, in the region of Analanjirofo ;The Gambia * Another name for

Banjul Banjul (, (US) and ), officially the City of Banjul, is the capital city of The Gambia. It is the centre of the eponymous administrative division which is home to an estimated 400,000 residents, making it The Gambia's largest and most densely ...

Island, in Banjul division {{Disambig