Megalomys is a genus of rodent in the family Cricetidae, part of the tribe Oryzomyini. The genus contains five large rodents from various Caribbean islands, all of which are now extinct. The last species to survive was M. desmarestii from Martinique, which became extinct after the Mount Pelée eruption in 1902.
It contains the following species:
- Extinct species section of the Joint Science department, Claremont college
- Turvey, S.T., Brace, S. and Weksler, M. A new species of recently extinct rice rat (Megalomys) from Barbados. Mammalian Biology - Zeitschrift für Säugetierkunde 77(6): 404–413.