Aegialomys species have a greyish to buff dorsal pelage which is divided sharply from the white to light yellow ventral pelage. They have relatively short ears. There are crowns of hair at the bases of the toes. The tail is equal to or longer than the body and is darker above than below.
There are two commonly recognized and described species in the genus, the mainland Yellowish Rice Rat (A. xanthaeolus), the type species, and the Galapagos Rice Rat (A. galapagoensis). There is however a third, undescribed species occurring on the Ecuadorean coast and the status of the two junior synonyms of A. xanthaeolus, ica Osgood, 1944 and baroni J.A. Allen, 1897, is currently unresolved. Also, the subspecies A. galapagoensis bauri is sometimes considered a separate species.
The genus currently comprises the following species: