Rajasaurus, which means "King lizard," is a carnivorous abelisaurid theropod dinosaur from the Late Cretaceous period in India. It consists of a single species, Rajasaurus narmadensis. The fossils were discovered in the Lameta Formation in Gujarat, located in Western India, in what is believed to have been the Narmada River Valley. In 2003 Rajasaurus was formally described based on a partial skeleton that included the braincase, spine, hip bone, legs, and tail. This discovery marked the first time an Indian theropod had been documented in such detail. Rajasaurus is estimated to have measured approximately 6.6 meters (22 feet) in length and featured a solitary horn on its forehead, likely employed for display and head-butting. Like other abelisaurids, Rajasaurus is believed to have been an ambush predator.

Rajasaurus possessed a short horn on its forehead, primarily composed of nasal bone rather than frontal bone, distinguishing it from the horn of Majungasaurus. The horn's size when alive likely matched its preserved size in fossils, unlike Carnotaurus, where the horn was extended in life by a thickened layer of skin. While Rajasaurus did have a thickened layer of skin, it probably did not contribute significantly to the overall length of the horn.

The horn of Rajasaurus might have served purposes such as display or engaging in head-butting contests with other Rajasaurus individuals. Head-butting behavior, inferred from the absence of shock-absorbing cancellous bone in the skull, could have involved either low-motion shoving matches akin to those of modern-day marine iguanas (Amblyrhynchus cristatus), or it might have been focused on the neck and flank, similar to the behavior of giraffes (Giraffa spp.). Nevertheless, the neck muscles of abelisaurids were adapted to withstand high stress. The horn could have been employed for defending territory or for competing in mating contests.

Abelisaurids are thought to have been ambush predators, employing a bite-and-hold strategy when hunting large prey. Majungasaurus and Rajasaurus both exhibited relatively shorter leg bones compared to theropods of similar size, suggesting they were relatively slower in terms of locomotion. However, ceratosaurs like Rajasaurus may have possessed the ability to rapidly accelerate.