Saint Helena (/ˌseɪnt həˈliːnə/ SAYNT-hə-LEE-nə), named after Saint Helena of Constantinople, is an island of volcanic origin in the South Atlantic Ocean. It is part of the British Overseas Territory of St Helena, Ascension and Tristan da Cunha, which also includes the Ascension Island and the islands of Tristan da Cunha. Saint Helena measures about 16 by 8 kilometres (10 by 5 mi) and has a population of 4,255 (2008 census).
The island was uninhabited when discovered by the Portuguese in 1502. One of the most isolated islands in the world, it was for centuries an important stopover for ships sailing to Europe from Asia and South Africa. The British also used the island as a place of exile, most notably for Napoleon I, Dinuzulu kaCetshwayo and more than 5,000 Boer prisoners. Saint Helena is Britain's second oldest remaining colony (now termed overseas territory), after Bermuda.