| Named By: | Scott Sampson in 1995 |
| Time Period: | Upper Cretaceous, 74.5-74 Ma |
| Location: | USA, Montana - Two Medicine Formation |
| Size: | About 4.5 meters long |
| Diet: | Herbivore |
| Fossil(s): | 3 skulls and several hundred bones from at least 15 individuals |
| Classification: | | Chordata | Reptilia | Dinosauria | Ornithischia | Ceratopsia | Ceratopsidae | Centrosaurinae | Pachyrhinosaurini | |
Einiosaurus is a medium-sized herbivorous centrosaurine ceratopsian dinosaur from the Upper Cretaceous (Campanian stage) of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian eini and Latinized Ancient Greek sauros; the specific name (procurvicornis) means 'with a forward-curving horn' in Latin.