Castanospermum australe (Moreton Bay Chestnut or Blackbean), the only species in the genus Castanospermum, is a flowering plant in the family Fabaceae, native to the east coast of Australia in Queensland and New South Wales, and to the Pacific islands of Vanuatu, New Caledonia, and the island of New Britain (Papua New Guinea). Members of this genus accumulate iminosugars in their leaves.