Prepotherium is an extinct genus of megatheriid ground sloths that lived during the Miocene period.

Fossils of Prepotherium have been found in the Collón Curá and Santa Cruz Formations of Argentina.

[1] Prepotherium differed from Megatherium by being smaller and having a less exaggeratedly convex inferior border of the lower jaw.

[2] An additional species from Venezuela, P. venezuelanum, was named by R. Collins in 1935.

[4] However, this species was later reclassified in its own genus, Pseudoprepotherium, as a basal member of another family of ground sloths, the Mylodontidae.