The species of the genus Erianthus StÅl, 1875 from Thailand and West Malaysia are revised. A key to the species is included, using the inner aspect of the male subgcnital lateral lobes as an additional useful diagnostic character. Five new species are described: Erianthus manueli sp.n., E. pyramidalis sp.n., E. serratus sp.n., E. inhamatus sp.n., and E. angulatus sp.n. First descriptions are given of the females of Erianthus guttatus (Westwood, 1842), E. rehni Descamps, 1975, E. fruhstorferi C. Bolívar, 1930, and E. versicolor Brunner, 1898. Faunistic data and a distribution map are added.