| Named By: | C. C. Young in 1939 |
| Time Period: | Middle Jurassic, Bathonian-Callovian |
| Location: | China - Sichuan Province - Dashanpu/Lower Shaximiao Formation. Possibly also the Upper Shaximiao though these remains are widely regarded as being indeterminate |
| Size: | Around 10 to just over 15 meters long. Full size depends upon the species |
| Diet: | Herbivore |
| Fossil(s): | Many individuals |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropoda | Mamenchisauridae | |
Omeisaurus (meaning "Omei lizard") is a genus of sauropod dinosaur from the Middle Jurassic Period (Bathonian-Callovian stage) of what is now China. Its name comes from Mount Emei, where it was discovered in the lower Shaximiao Formation of Sichuan Province.
Like other sauropods, Omeisaurus was herbivorous and large. It measured 20.2 metres (66 ft) long, and weighed 9.8 tonnes.