An artist's illustration of "Megacervixosaurus tibetensis"
"Megacervixosaurus" (meaning "big neck lizard") is the informal name given to an as yet undescribed genus of sauropod dinosaur from the Late Cretaceous. It was a sauropod which lived in what is now China. The type species, "Megacervixosaurus tibetensis", was coined by Chinese paleontologist Zhao Xijin in 1985.
"Megacervixosaurus" may have been a diplodocid, but it has never been formally described, and remains a nomen nudum.