A skull and partial skeleton of a new genus and species, Monolophosaurus jiangi n.gen., n.sp., of large theropod has been recovered from the Middle Jurassic beds in the Junggar Basin of Xinjiang, China. The most striking characteristic is a crest, formed primarily by the nasal and lacrimal bones, on the midline of the skull. Several foramina connect the hollow interior of the crest with the antorbital fossa. The function of the crest is unknown, although it most likely was used for visual recognition by other members of the same species. It is difficult to make a precise taxonomic assignment in the absence of information on the appendicular skeleton, but it appears to be more closely related to Allosaurus than to other megalosaur grade theropods.