The taxonomy of the genus Tethya from Brazil is revised. Five species are described, four of which are new to science: Tethya maza, T. beatrizae sp. nov., T. nicoleae sp. nov., T. parvula sp. nov., and T. solangeae sp. nov. Five earlier records of Tethya from Brazil (T. aurantium, T. diploderma, T. maza, T. japonica and T. seychellensis) are re-evaluated and only T. maza is confirmed. The other previous records of Tethya from Brazil, viz., Tethya brasiliana, T. cyanae, T. ignis and T. rubra, have been recently described in detail using scanning electron microscopy and are also considered valid. An amendment to the nomenclature of micrasters is made, recognizing at least two different morphologies of each type of micraster (strongylasters types 1 and 2, tylasters types 1 and 2, and oxyasters types 1, 2 and 3). A neotype was designated for T. maza. With four new species described here and four previous records considered invalid the known diversity of Tethya in Brazil still remains nine species. However, its rate of endemism has increased from 44% to 89%.
