A taxonomic account is presented for the species of Massonia recorded from the core Cape Floristic Region. A total of 15 species are recognised, 13 endemic to the region, distributed between sect. Whiteheadia and sect. Massonia. Several species are local endemics known from a single locality or restricted area, although M. bifolia and M. depressa are widely distributed through much of the Greater Cape Floristic Region or even beyond into interior South Africa. All published names based on plants known to have been collected within the core CFR are accounted for, and several new synonyms are identified, including two earlier names for more recently described species, with M. citrina M.Pinter et al. (2013) considered to be a synonym of M. triflora Compton (1931), which is recognised as a species distinct from M. depressa Houtt., and M. dregei Baker (1879) identified as an earlier name for Neobakeria visserae P.E.Barnes (1933). A full description and nomenclature are provided for each species, with notes on distribution and ecology, as well as an identification key to the species. Most species are illustrated.