Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. Ground sloths are a paraphyletic group, as living tree sloths are thought to have evolved from ground sloth ancestors. Ground sloths varied widely in size, with the largest genera Megatherium and Eremotherium being around the size of elephants.

The early evolution of ground sloths took place during the late Paleogene and Neogene of South America, while the continent was isolated. At their earliest appearance in the fossil record, the ground sloths were already distinct at the family level. Sloths dispersed into the Greater Antilles during the Oligocene, and the presence of intervening islands between the American continents in the Miocene allowed a dispersal of some species into North America, They were hardy as evidenced by their diverse numbers and dispersals into remote areas given the finding of their remains in Patagonia (Cueva del Milodón Natural Monument) and parts of Alaska. Sloths, and xenarthrans as a whole, represent one of the more successful South American groups during the Great American Interchange after the connection of North and South America during the late Pliocene with a number of ground sloth genera migrating northwards.

Ground sloths abruptly became extinct on the American mainland as part of the Quaternary extinction event at the end of the Pleistocene, around 12,000 years ago along with most other large mammals in the Americas. Their extinction has been posited to be the result of hunting by recently arrived humans and/or climate change. A number of kill sites are known where humans butchered ground sloths dating just prior to their extinction.

The Caribbean ground sloths, the most recent survivors, lived in the Antilles, possibly until 1550 BCE. However, radiocarbon dating suggests an age of between 2819 and 2660 BCE for the last occurrence of Megalocnus in Cuba. They survived 5,000–6,000 years longer in the Caribbean than on the American mainland, which correlates with the later colonization of this area by humans.