Yangchuanosaurus is a genus of metriacanthosaurid theropod dinosaur that lived in China during the Bathonian and Callovian stages of the Middle Jurassic, and was similar in size and appearance to its North American relative, Allosaurus. It hails from the Upper Shaximiao Formation and was the largest predator in a landscape which included the sauropods Mamenchisaurus and Omeisaurus as well as the Stegosaurs Chialingosaurus, Tuojiangosaurus and Chungkingosaurus. It got its name after its discovery site in Yongchuan, in China.
The type specimen of Y. shangyouensis had a skull 82 cm (2.7 ft) long, and its total body length was estimated at about 8 m (26 ft). Another specimen, assigned to the new species Y. magnus, was even larger, with a skull length of 1.11 m (3.6 ft). It may have been up to 10.8 m (35.4 ft) long, and weighed as much as 3.4 metric tons (3.7 short tons). There was a bony ridge on its nose and multiple hornlets and ridges, similar to Ceratosaurus.
Yangchuanosaurus was a large, powerful meat-eater. It walked on two large, muscular legs, had short arms, a strong, short neck, a big head with powerful jaws, and large, serrated teeth. It had a long, massive tail that was about half of its length. Its feet had three toes, each with a large claw. Its arms were short.
Yangchuanosaurus zigongensis is known from four specimens including ZDM 9011 (holotype), a partial postcranial skeleton; ZDM 9012, a left maxilla; ZDM 9013, two teeth and ZDM 9014, a right hind limb. It was first described by Gao (1993), and all specimens were collected from the Middle Jurassic Xiashaximiao Formation in the Dashanpu Dinosaur Quarry of Zigong, Sichuan. A phylogenetic analysis by Carrano et al. (2012) found Yangchuanosaurus to be the basalmost known metriacanthosaurid and the only non-metriacanthosaurine metriacanthosaurid.