An account of species of the genera Aptosimum and Peliostomum occurring in Namibia is presented, together with an updated key for all accepted species of these genera. The sinking of Peliostomum in Aptosimum is discussed and rejected. A new species from Namibia, Aptosimum radiatum, is described. Species descriptions, global and Namibian distributions, conservation status, habitat and phenological information are presented for the 16 Aptosimum and three Peliostomum species recognised from Namibia. The type for Peliostomum is designated. Arguments are presented for the choice of one neotype for an accepted species, as well as 29 lectotypes: 15 for names of accepted species, 14 for synonyms. Keywords: Generic concept, keys, lectotypification, neotypification, taxonomy.