Bruny Island is a 362-square-kilometre (140 sq mi) island located off the southeastern coast of Tasmania, Australia. The island is separated from the Tasmanian mainland by the D'Entrecasteaux Channel, and its east coast lies within the Tasman Sea. Located to the island's northeast Storm Bay, is the river mouth to the Derwent River estuary, and serves as the main port of Hobart, Tasmania's capital city. Both the island and the channel are named after French explorer, Antoine Bruni d'Entrecasteaux. Its traditional Aboriginal name is lunawanna-allonah, which survives as the name of two island settlements, Alonnah and Lunawanna.