"Katsuyamasaurus" (meaning "Katsuyama lizard") is the informal name given to an as yet undescribed genus of theropod dinosaur from the Early Cretaceous. It was a carnosaur which lived in what is now Japan. The type species was coined by Lambert in 1990, but is not formally described, making it a nomen nudum. "Katsuyamasaurus" is known from remains including an ulna and a vertebra, and is named after the locality in Japan where the fossils were found. After the publication of Fukuiraptor, George Olshevsky suggested that "Katsuyamasaurus" could be a synonym, but a formal synonymization has not yet occurred.