| Named By: | Jose Fernando Bonaparte in 1967 |
| Time Period: | Late Triassic, 227-213 Ma |
| Location: | Argentina, La Rioja Province - Los Colorados Formation |
| Size: | About 10 meters long |
| Diet: | Herbivore |
| Fossil(s): | Several individuals |
| Classification: | | Chordata | Reptilia | Dinosauria | Saurischia | Sauropodomorpha | Prosauropoda | Riojasauridae | |
Riojasaurus (meaning "Rioja lizard") was a herbivorous sauropodomorph dinosaur named after La Rioja Province in Argentina where it was found by Jose Bonaparte. It lived during the Late Triassic and grew to about 10 metres (33 ft) long. Riojasaurus is the only known riojasaurid to live in South America.