Mormosaurus ("Mormo's Lizard") is an extinct genus of tapinocephalid dinocephalian therapsid from the Guadalupian epoch of South Africa. It was first named by Watson in 1914, and contains one species, M. seeleyi. Individuals of Mormosaurus had a long skull. Its taxonomic status is not settled, as Mormosaurus may be congeneric with Tapinocephalus.