| Named By: | M. E. Perez in 2010 |
| Time Period: | Mid Miocene (Laventan)~13.8-11.8 Ma |
| Location: | Argentina. Bolivia. Peru |
| Size: | Unavailable |
| Diet: | Herbivore |
| Fossil(s): | Partial remains |
| Classification: | | Chordata | Mammalia | Rodentia | Hystricomorpha | Hystricognathi | Caviomorpha | Cavioidea | |
Guiomys is an extinct genus of cavioid rodent which lived in west central Patagonia of Argentina (Collon Cura Formation), Bolivia (Honda Group) and Peru (Yahuarango Formation) during the Middle Miocene (Laventan). Guiomys is known from mandibular and maxillary fragments with molars, and isolated cheek teeth. It was first named by Maria E. Perez in 2010 and the type species is Guiomys unica.