Arctotherium is an extinct genus of South American short-faced bears within Ursidae of the Pleistocene. Their ancestors migrated from North America to South America during the Great American Interchange, following the formation of the Isthmus of Panama during the late Pliocene. The oldest remains are from the Ensenadan epoch within the early-middle Pleistocene 1.2 Mya. Their closest known relative is the spectacled bear (Tremarctos ornatus).