The new species Begonia samhaensis, in section Peltaugustia (Warb.) Barkley, is described from the island of Samha in the Socotra archipelago. It differs from the only other species in the section, B. socotrana Hook.f., in a number of gross morphological characters and is likely to be a relict taxon rather than the result of more recent dispersal and divergence. A revision of sect. Peltaugustia is presented. Detailed surveys have been carried out on both species. The new species has a restricted distribution and a total population of fewer than 1000 individuals, and is recommended to be placed in the IUCN category VU D1, 2. Begonia socotrana has been found in new sites, and is locally common in parts of its range. Its current placing in the IUCN ‘Vulnerable’ category is considered to be unwarranted, and it is recommended that the species should be listed as ‘Least Concern’.