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), and was renamed by George Olshevsky in 1991. Protognathosaurus is known only from a fragmentary jaw.