Protognathosaurus (meaning "early jaw lizard") is a genus of dinosaur from the Middle Jurassic. It was a sauropod found in what is present-day China. The type species, P. oxyodon, was originally described by Zhang (1988) (as Protognathus, which was already in use for a genus of beetle), and was renamed by George Olshevsky in 1991. Protognathosaurus is known only from a fragmentary jaw.