A city and administrative region of southeast China on the coast southeast of Guangzhou, including Hong Kong Island and adjacent areas. Hong Kong Island was occupied by the British during the Opium War (1839-1842) and ceded to them by the Treaty of Nanking (1842). Other portions of the colony were acquired in 1860 and in 1898 by a 99-year lease. Hong Kong reverted to Chinese sovereignty in 1997. It is a major port and a center of international commerce and banking.