| Named By: | Edward Drinker Cope in 1872 |
| Time Period: | Late Eocene |
| Location: | USA |
| Size: | Up to 4 meters long, 2.1 meters high at the shoulder |
| Diet: | Herbivore |
| Fossil(s): | Few specimens |
| Classification: | | Chordata | Mammalia | Dinocerata | Uintatheriidae | |
| Also known as: | | Uintacolotherium | |
Eobasileus cornutus ("crowned dawn-king") was a prehistoric species of dinocerate mammal.
Eobasileus was 4 metres (13 ft) long and stood 2.1 metres (6.9 ft) tall at the shoulder; and with a weight up to 4000 kg (8818 lbs) it was the largest uintathere. It looked very similar to the related Uintatherium. Like Uintatherium, it had three pairs of blunt horns on its skull, possibly covered with skin like the ossicones of a giraffe. The frontal pair may have been composed of keratin, like the horn(s) of a rhinoceros. Eobasileus also had a pair of tusks which were shielded by bony protrusions of the lower jaw.
It is still debated among scientists if Eobasileus and other Uintatheres were in fact related to rhinos, it is possible that the uintatheres were related to the modern day rhino, but most prehistoric rhinos in the Eocene where much smaller than Eobasileus.