Based on new material from the top of the Late Jurassic Shangshaximiao Formation of Xiaogu, Qianwei County, southwestern Sichuan Basin, a new sinraptorid carnosaur Leshansaurus qianweiensis gen. et sp. nov. is erected. It is distinguished from other carnosaurs by supraoccipital with a sharp midline ridge; relatively longer frontal with a ratio of the maximum length to the maximum width about 2.86; basipterygoid processes of basisphenoid slender; atlantal intercentrum horseshoe-shaped; diapophyses of dorsal vertebrae relatively slender; neural spines of dorsal and sacral vertebrae very thin; ventral keel of sacral vertebrae distinctly defined; ilium with a conspicuous ridge medially along acetabular edge. This new dinosaur was the latest carnosaur presently known in Sichuan Basin. Its discovery extends the horizontal and geographical distributions of the carnosaurs in Sichuan Basin, and is significant in the evolution of the carnosaurs.