Yunnanosaurus (YOU-NAN-oh-SAWR-us) is a genus of prosauropod dinosaur from the Early Jurassic period; a position in time that makes it one of the last prosauropods.

It is closely related to Lufengosaurus. It was approximately 7 metres (23 ft) long and 2 metres (7 ft) high. It is known from twenty skeletons, including two skulls, recovered from the Lufeng Formation ofYunnan, China. Yunnanosaurus was unique among prosauropods in that its teeth were self-sharpening. There were more than sixty of these spoon shaped teeth in the jaws of Yunnanosaurus. Scientists consider these teeth to be advanced compared to other prosauropods. They share features with the sauropods'.

However, scientists do not consider Yunannosaurus to be especially close to the sauropods in phylogeny because the remaining portions of the animals body are distinctly prosauropod in design. The similarity in dentition between Yunnanosaurus and sauropods might be an example of Convergent Evolution. (Convergent evolution describes the process whereby organisms not closely related independently evolve similar traits as they both adapt to similar environments. On a molecular level, this can happen due to random mutation unrelated to adaptive changes.)

Yunnanosaurus was a large plant-eating dinosaur during the Hettangian-Pliensbachian ages, about 208-194 million years ago. This primitive sauropodomorph had a long neck, long tail, and a small, narrow head with a short snout.