Gigantosaurus (meaning "giant lizard") is a poorly known sauropod dinosaur genus from England. The type species, Gigantosaurus megalonyx, was named and described by Harry Govier Seeley in 1869. Its type, consists of several separately discovered sauropod bones found near Stretham,England, among which two casts of the "large claw" the specific name, derived from Greek megalos and onyx.