island in the northern end of Hauraki Gulf, eastern North Island, New Zealand, lying 15 miles (24 km) across Jellicoe Channel from the mainland. Cradock Channel separates it from Great Barrier Island to the east. Of volcanic origin, the island has a total land area of 11 square miles (28 square km). Its generally wooded surface rises steeply to 2,370 feet (722 m) in Mount Hauturu, the flanks of which are cut by deep ravines.

Captain James Cook (Cook, James) named the island in 1769, and it was bought by the British government in the 1880s. The island is a wildlife sanctuary without permanent inhabitants; visitors must procure a permit to land from the Department of Conservation.