Chief island (pop., 1995 est.: 456,934) of Tanzania.
Located in the Indian Ocean off the coast of east-central Africa, it has an area of 637 sq mi (1,651 sq km). Zanzibar city (pop., 1988: 157,634), the island's principal port and commercial centre, is on the western side. Both Zanzibar and Pemba islands are believed to have once formed part of the African continent. In the late 17th century it came under the control of Omani Arabs, and the sultan of Oman made Zanzibar city his capital in 1832. In 1861 Zanzibar was separated from Oman and became an independent sultanate composed of the island, Kenya, Mafia Island, and the coasts of Tanzania and Somalia. Under Sultan Barghash (r. 1870–88), most of the mainland territories were lost to European powers. In 1890 the British proclaimed a protectorate over Zanzibar and Pemba islands. In 1963 the sultanate regained its independence and became a member of the Commonwealth . The sultanate was overthrown in 1964, and a republic was established. It then joined with Tanganyika to form the Republic of Tanzania. The economy depends on agriculture and fishing.