| Named By: | Gideon Mantell in 1850 |
| Time Period: | Early Cretaceous, 132 Ma |
| Location: | England - Lower Greensand Group, Wealden Group, and France |
| Size: | Estimated about 16 meters long |
| Diet: | Herbivore |
| Fossil(s): | Various partial post cranial remains |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropoda | Brachiosauridae | |
| Also known as: | | Cetiosaurus conybeari | |
Pelorosaurus ( pa-LORR-oh-SOR-as; meaning "monstrous lizard") is the generic name of a sauropod dinosaur. Pelorosaurus was one of the first sauropod names ever. Remains referred to Pelorosaurus date from the Early Cretaceous period, about 140-125 million years ago and have been found in England and Portugal.
Many species have been named in the genus but today these are largely seen as belonging to other genera. The first named species of Pelorosaurus, P. conybeari, is a junior synonym of Cetiosaurus brevis.