Viscacha rats are a group of rodents in the family Octodontidae. All species are found in Argentina. They are placed in the following genera:
Genus Octomys O. mimax , mountain viscacha rat, found in the Andes Genus Pipanacoctomys P. aureus, the golden viscacha rat, found near a salt flat Genus Tympanoctomys (4 species, 3 extant), found in desert shrubland near salt flats T. barrerae, the plains viscacha rat T. kirchnerorum, Kirchner's viscacha rat, T. loschalchalerosorum, the Chalchalero viscacha rat †T. cordubensis
