| Named By: | Georges Cuvier in 1796 |
| Time Period: | Early Pliocene[1] to Early Holocene, 5-0.010 Ma Possible later date of 0.008 Ma |
| Location: | South America |
| Size: | 6 meters long |
| Diet: | Primarily a herbivore, but possibly omnivorous |
| Fossil(s): | Many fossil specimens allowing for complete reconstruction |
| Classification: | | Chordata | Mammalia | Xenarthra | Pilosa | Megatheriidae | |
Megatherium ( meg-a-THEER-ee-am from the Greek mega [megas], meaning "great", and therion [therion], "beast") was a genus of elephant-sized ground sloths endemic to South America, sometimes called the giant ground sloth, that lived from the Early Pliocene through the end of the Pleistocene. Among land mammals, its size was exceeded by only a few other species, including mammoths and the much older Paraceratherium.