Promegatherium ("Before Megatherium") is an genus of prehistoric xenarthrans that lived in South America, primarily Argentina, during the Middle to Upper Miocene. This genus is regarded as closely related to the later, and more famous genus, Megatherium, hence the reference in the name. The first specimens of Promegatherium were originally described by the biologist Florentino Ameghino in 1887. Its known species are Promegatherium cabreri, P. nanum, P. parvulum, P. remulsum, and P. smaltatum. P. nanum was originally placed in the genus "Eomegatherium" before it was grouped together in Promegatherium.