Long Island is an elongated island of 73 hectares in the Hawkesbury River, about 50 kilometres (31 mi) north of Sydney, New South Wales, Australia. It is joined to the mainland at its south eastern edge by the railway causeway across Sandbrook Inlet. At the other end of this causeway is the Sydney suburb of Brooklyn in Hornsby Shire, to which Long Island belongs. Other islands in the Hawkesbury River include Dangar Island, Spectacle Island, Milson Island, Peat Island and Lion Island. Long Island was added to the Australian National Heritage List in December 2006.