Spinosaurus (meaning "spine lizard") is a genus of theropod dinosaur which lived in what is now North Africa, from the Albian to early Cenomanian stages of the Cretaceous period, about 100 to 97 million years ago.

The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew up to 2 meters (7 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that they were covered in muscle and formed a hump or ridge. Multiple functions have been put forward for this structure, including thermoregulation and display.

According to recent estimates, Spinosaurus is the largest of all known carnivorous dinosaurs, even larger than Tyrannosaurus rex and Giganotosaurus. These estimates suggest that it was around 16 to 18 metres (52 to 59 ft) in length and 7 to 9 tonnes (7.7 to 9.9 short tons) in weight.