The New Ireland forest rat (Rattus sanila) is a large rodent in the family Muridae. It is endemic to New Ireland, in the Bismarck Archipelago, Papua New Guinea.
Rattus sanila is known only by the discovery of some 7 subfossil fragments of jaw dated to over 3,000 years old. The molars of this particular species are broad and have a very complex structure of the cusp. The diastema is also longer than in other species of the genus Rattus suggesting a separate species which may be a relict of an archaic or ancestral dispersal of Rattus stock to New Guinea and Australia. This species probably still survives in some primary forest.