Gigantspinosaurus is a genus of stegosaur dinosaur belonging to the group Stegosauridae. It lived during the Early Jurassic period, approximately 174 to 168 million years ago. The first fossils of Gigantspinosaurus were discovered in the Dashanpu Formation of China, in the Sichuan Province.

Gigantspinosaurus was a relatively large stegosaur, measuring up to 20 feet (6 meters) in length. As a member of the Stegosauridae group, it shared some common features with its stegosaur relatives, including a small head with a beak-like mouth, and a massive, barrel-shaped body. Gigantspinosaurus is the first known member of the Stegosauria.

The most striking characteristic of Gigantspinosaurus was its impressive array of long spikes along its back. These spikes, known as dorsal plates, varied in size, with the largest spikes situated over the hips. The function of these unique plates remains a subject of scientific debate, with theories ranging from thermal regulation to defensive displays.

Gigantspinosaurus boasts a unique appearance, featuring relatively small dorsal plates and significantly enlarged shoulder spines known as spinae parascapulares, twice the length of the shoulder blades, supported by large leveled bases. The neck plates are small and triangular, while the head likely had a considerable size, with thirty teeth present in each lower jaw. Notably, its hips are notably broad, and the four sacral vertebrae and the initial tail vertebra possess fused low neural spines, forming a single plate. Additionally, strong forelimbs were among its distinguishing features.