| Named By: | Charles Alfred Matley & Friedrich von Huene in 1933 |
| Time Period: | Late Cretaceous, 69 Ma |
| Location: | India |
| Size: | Uncertain due to lack of fossil remains |
| Diet: | Carnivore |
| Fossil(s): | Partial skull, as well as further partial post cranial remains attributed to the genus |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Theropoda | Abelisauridae | |
| Also known as: | | Megalosurus matleyi | |
Indosaurus (meaning "Indian lizard") is a genus of theropod dinosaur once living in what is now India. It lived approximately 69 million years ago, in the Maastrichtian division of the Late Cretaceous. It weighed roughly 700 kg (1540 lb).
The fossil evidence from Jabalpur, India, includes the now-lost holotype GSI K27/565, a partial skull of unusual thickness found by Charles Alfred Matley in the Lameta Formation; other parts of the skeleton have later been referred to it. The cranium suggests that Indosaurus may have had horns above its eyes, although all the fossil evidence has since been lost. Indosaurus may have been related to the unusual South American dinosaur, Carnotaurus. If this is the case then India had not been a separate continent for the previous 100 million years, as many paleontologists had thought. It is possible instead that the two land masses were connected intermittently by land bridges, allowing dinosaurs from both areas to migrate.
The type species, Indosaurus matleyi, was named by Huene and Matley in 1933. The generic name refers to India. The specific name honours Matley. This species now also includes Megalosaurus matleyi; confusingly, the dubious tooth taxon Orthogoniosaurus shares the same specific name (but is based on different material). Some paleontologists have speculated that Indosuchus and Compsosuchus should also be included within Indosaurus.
Originally assigned by Huene to the Allosauridae, Indosaurus is today considered a member of the Abelisauridae.