A description of Nomingia gobiensis gen. et sp. n., the first known dinosaur with a pygostyle, the structure known so far only in birds, is presented. The specimen comes from the Late Cretaceous strata at Bugin Tsav, Trans-Altai Gobi, Mongolia. N. gobiensis is assigned within the Oviraptorosauria based on the following characters: pneumatized caudal vertebrae, posteriorly concave ischium, and deep cervicodorsal hypapophyses. This specimen has been previously partially described without being formally named (Barsbold et al. 2000).