Six island or island groups (Marion and Prince Edwards Islands, Iles Crozet, Iles Kerguelen, Heard and McDonald Islands, Macquarie Island, South Georgia) are considered in this account to belong to the sub-Antarctic region. The environments and biota of these islands are described. The vulnerability of their indigenous floras and faunas to introduced alien species is stressed. The sovereignty and administration of the islands and the conservation issues pertaining to them are discussed. Currently, less than 4% of the terrestrial sub-Antarctic is under statutory protection. Conservation and protection of the sub-Antarctic islands must be based on consideration of the conservation of the southern ocean as a whole.