Gigantosaurus (meaning "giant lizard") is a sauropod dinosaur that lived in England during the Jurassic period. The type species, Gigantosaurus megalonyx, was named and described by Harry Govier Seeley in 1869. The known Gigantosaurus fossils are incomplete. They include just: sacral vertebra, radius, fibula and tibia. The bones of Gigantosaurus are separately discovered.