The first worldwide revision of the wasp genus Ufens Girault, 1911 (Hymenoptera: Trichogrammatidae: Oligositinae) is presented. Ufens is known to parasitize primarily hemipteran eggs and is a cosmopolitan genus most common in temperate and semi-arid regions such as the southwestern United States and Australia. Forty-three species are recognized here. Included in the revision are five species formerly in the genus Ufensia, herein synonymized, and 32 new species. In addition, seven species are removed from Ufens and placed in renewed combination in Mirufens. Because thirteen nominal species...