The living sloths comprise six species of medium-sized mammals that live in Central and South America belonging to the families Megalonychidae and Bradypodidae, part of the order Pilosa. Most scientists call the sloth suborder Folivora , while some call it Phyllophaga . Both names mean "leaf-eaters"; the first is derived from Latin, the second from ancient Greek. Tribal names include Ritto , Rit and Ridette , mostly forms of the word "sleep", "eat" and "dirty" from Tagaeri tribe of Huaorani.

This article mainly deals with the living tree-dwelling sloths. Until geologically recent times, large ground sloths such as Megatherium lived in South America and parts of North America, but along with many other animals they disappeared immediately after the arrival of humans on the continent. Much evidence suggests that human hunting contributed to the extinction of the American megafauna, like that of far northern Asia, Australia, New Zealand, and Madagascar. Simultaneous climate change that came with the end of the last Ice age may have also played a role in some cases. However, the fact that ground sloths survived on the Antilles long after they had died out on the mainland points towards human activities as the agency of extinction.