The Mydidae genera Namibimydas Hesse, 1972 and Nothomydas Hesse, 1969 are reviewed. Both genera were known from two species each occurring in southern Namibia and western South Africa and are here redescribed. Four new species, all from Namibia, are described herein: Namibimydas psamminos sp. n., Namibimydas stuckenbergi sp. n., Nothomydas aquilonius sp. n., and Nothomydas picketti sp. n. A dichotomous key to all species is presented and illustrations and photographs are provided to support the descriptions and future identification. Distribution, occurrence in biodiversity hotspots sensu Conservation International, and seasonal incidence are discussed for all species. Information of all four genera of Syllegomydinae: Halterorchini is summarised and photographs of all genera provided. A novel structure of the male terminalia, termed supra-hypandrial sclerite, is described and illustrated.