The fossorial giant rat (Gyldenstolpia fronto) is a species of rodent in the family Cricetidae.

[2] It is found in Argentina and Brazil but was determined extinct following a recent assessment of the conservation status of Sigmodontine rodents.

[3] Its natural habitat is assumed to be dry savanna, but there have been no ecological details reported.

[4] It was previously considered part of the genus Kunsia but is now recognized in the genus Gyldenstolpia, a subset of Sigmodontine rodents known only from a few fossils and recent specimens found in central South America.

Defining characteristics of G. fronto include a robust skull with a restricted interorbital region; rounded, somewhat hidden ears; thick bristle-like dorsal hair, small eyes, and a short tail relative to overall body length.