Gigantspinosaurus (meaning "giant-spined lizard") is a genus of dinosaur from the Late Jurassic. It was a stegosaur found in the Upper Shaximiao Formation of Zigong, Sichuan, China, and is known from a partial skeleton missing the skull (except for the lower jaw), hind feet, and tail. The type species, Gigantspinosaurus sichuanensis, was described in 1992, but was generally considered a nomen nudum, until 2006. Despite its questionable nomenclatural status, images of Gigantspinosaurus have appeared in several sources, and a mounted skeleton has been on display in Zigong since 1996. Gigantspinosaurus has a distinctive appearance with relatively small dorsal plates and greatly enlarged shoulder spines, twice the length of the shoulder blades. Recent research indicates that Gigantspinosaurus is the most basal known member of Stegosauria. It is estimated to have been about 4 metres long.
Size of Gigantspinosaurus, compared to a human.Public awareness of this animal was increased in early 2006 when Tracy Ford, considering it a validly established taxon, published a short article on reconstructing it. Ford suggested that earlier reconstructions of Gigantspinosaurus attached the shoulder spines upside-down, and his new reconstruction shows the spine extending somewhat upwards, ending higher than the top of the animal's back. Susannah Maidment and Guangbiao Wei (2006) treated G. sichuanensis as a valid taxon in their review of Late Jurassic Chinese stegosaurs, but did not redescribe it because it is currently under study by Zigong Dinosaur Museum staff.