A large-bodied (skull length 775 mm) elasmothere rhinoceros was discovered in the early late Miocene (equivalent to the European Vallesian) Liushu Formation of the Linxia Basin in northwestern China. Iranotherium morgani, represented by two skulls and a mandible, is the only known rhinoceros with a rugosity on each zygomatic arch of the male individual. Such a unique cranial feature is otherwise unknown among rhinoceroses. Numerous cranial and dental characteristics indicate that Iranotherium morgani is a member of Elasmotheriini, an enigmatic clade of Rhinocerotinae. The large, robust areas on the zygomas of the male Iranotherium, for larger masseteric and temporalis musculature, suggest that these rhinoceroses were sexually dimorphic, probably similar to their artiodactyl counterparts in an open grassland fauna.