Six species have been described for the genus Orinus Hitchc. (Poaceae). Our analyses of morphological and genetic variation at the population level indicate that the genus should be reduced to three species, one of which, O. intermedius X. Su & J. Quan Liu, we describe as new from the Qinghai-Tibet Plateau. We include a complete taxonomic revision of the genus, a key to distinguish the three species, and geographic distribution and habitat data for each species.