Ceratosaurus is a genus of theropod dinosaur belonging to the group Ceratosauridae. It lived during the Late Jurassic period, approximately 150 to 144 million years ago. The first fossils of Ceratosaurus were discovered in Colorado, USA, in the late 19th century. It name is originated from its distinct features: a blunt horn at the tip of its snout.

Ceratosaurus was a large theropod dinosaur, measuring around 20 to 23 feet (6 to 7 meters) in length and weighing approximately 1,500 to 2,000 pounds (700 to 900 kilograms). It was characterized by its robust build, powerful hind limbs, and a distinctive horn-like structure on its snout. Ceratosaurus had a relatively large skull compared to the rest of its body, measuring 55 cm (22 in) in length. Down the middle of its neck, back, and tail, a row of small osteoderms (skin bones) was present. Additionally, other osteoderms were found in unknown positions on its body.

One of the most notable aspects of Ceratosaurus was its nasal horn, projecting from the front of its snout. Alongside the nasal horn, it had two small horns above its eyes, and some individuals might have sported a bony frill or crest on the back of the head. These unique features distinguish Ceratosaurus from other theropod dinosaurs. While the exact purpose of these horns remains unclear, it can be inferred that they were not intended for defensive purposes due to their relatively small size.