The genus Desimia Reitter, 1882 of the ant-loving beetle tribe Ctenistini (Staphylinidae: Pselaphinae) previously contained 24 species distributed in the Afrotropical and Western Palearctic realms. In this study, Desimia orientalis Zhang and Yin, new species is described based on two males collected from the southern Chinese provinces of Guizhou and Guangxi, supported by illustrations of the habitus and other morphological details. The species is characterized by a simple maxillary palpomere 2, combined with the unique shape of the four-segmented male antennal club and aedeagus. A map showing the worldwide distribution of Desimia is included.