Hypogeomys is a genus of nesomyids in the family Nesomyidae, found in Madagascar. There is one extant species, the Malagasy giant rat (Hypogeomys antimena), currently an endangered species with a restricted range. There is also another species known from subfossils from a few thousand years ago, Hypogeomys australis. The malagasy giant rat measures 33 centimetres (13 in), making it the largest rodent in Madagascar, while Hypogeomys australis seems to have been slightly larger.