The Hainan black-crested gibbon or Hainan gibbon (Nomascus hainanus), is a species of gibbon found only on Hainan Island, China. It was formerly considered a subspecies of the eastern black crested gibbon (Nomascus nasutus) from Hòa Bình and Cao Bằng provinces of Vietnam and Jingxi County in Guangxi Zhuang Autonomous Region, China. Molecular data, like morphology and call differences, suggest it is a separate species. Its habitat consists of broad-leaved forests and semideciduous monsoon forests. It feeds on ripe, sugar-rich fruit, such as figs (Ficus spp.) and, at times, leaves, and insects.