Amtosaurus (; "Amtgai lizard") is a genus of ornithischian dinosaur based on a fragmentary skull collected from the Upper Cretaceous Bayan Shireh Formation (Cenomanian to Santonian) of Mongolia and originally believed to represent an ankylosaurid.[1] Hadrosaurid affinities have also been suggested. However, per Parish and Barrett, this specimen is too fragmentary to be reliably classified beyond an indeterminate ornithischian. A second species assigned to the genus, A. archibaldi, has become the basis of a valid ankylosaurid taxon, Bissektipelta.[2]