Garden Island is an island in the Australian state of South Australia located about 14 kilometres (8.7 mi) north-west of the capital city of Adelaide in an estuary system within the Adelaide metropolitan area which drains into Gulf St Vincent. It is notable as being a site for a mangrove forest, a landfill, a part of the site for the Multifunction Polis, a ship graveyard and a venue for recreational boating activities. It has enjoyed varying degrees of protected area status since 1973.