Uintatherium ("Beast of the Uinta Mountains") is an extinct genus of herbivorous dinoceratan mammal that lived during the Eocene epoch.

The upper canine teeth were large and may have been formidable defensive weapons;[2] superficially, they resembled those of saber-toothed cats.

In August 1872, Leidy named Uintatherium robustum based on a posterior skull and partial mandibles (ANSP 12607).

[6][7] Another specimen discovered by Leidy's crews consisting of a canine was named Uintamastix atrox and was thought to have been a saber-toothed and carnivorous.

[10][11] Because of Cope and Marsh's rivalry, the two would often publish scathing criticisms of each other's work, stating their respective genera were valid.

[6] Many additional discoveries of Uintatherium have since occurred, making it one of the best-known and popular American fossil mammals.

[12][6] Princeton University launched expeditions to the Eocene beds of Wyoming in the 1870s and 1880s, discovering several partial since skulls and naming several species of uintatheres that are now considered synonyms of U.