Banaba (bənäˈbə) [key] or Ocean Island, island (1990 pop. 284), 2.2 sq mi (5.7 sq km), central Pacific, in the Republic of Kiribati, in the Gilbert Islands. The island was first visited by the British in 1804, was annexed in 1900, and from 1907 was the administrative capital of the Gilbert and Ellice Islands until World War II. The inhabitants are largely Micronesians. Banaba had important phosphate deposits, but mining was discontinued in 1979.