Cranial, dental, and postcranial remains of the bush dog, Speothos pacivorus (Lund, 1839) are described from deposits of late Pleistocene-Holocene age in the Lagoa Santa Caves, Minas Gerais, Brazil. This species can be distinguished from the extant S. venaticus, on the basis of larger size, presence of metaconule and hypocone on M1, large M2, and double-rooted M2. Re-evaluation of the phylogenetic relationships of South American canids suggests that Speothos is a member of the Cerdocyon clade (including Cerdocyon, Nyctereutes, Atelocynus, and Speothos) and is most closely related to the small-eared dog, Atelocynus. The biogeographic history of the bush dog suggests that it is the product of speciation in South America, probably in the Brazilian highlands during the late Pleistocene and Holocene.