A survey is presented of past treatment of the genus Ctenitis C. Chr. in the Old World, with the conclusion that the genus has not hitherto been clearly defined. A new generic description covering the species of Asia, Malesia and the Western Pacific is presented, with a new division of the species into two subgroups of informal status, based on scales and spores, and a key to all species. Seventeen new species are described, one new name proposed and four new combinations made. A list of species in the region which, in the opinion of the author, have been wrongly included in Ctenitis, is appended.