Engystoma olivaceum Gastrophryne olivacea, the Great Plains narrow-mouthed toad or western narrow-mouthed toad, is a species of microhylid frog found throughout much of the south-central United States from Nebraska south through Texas, and into northern Mexico.

Though not a true toad, evidenced by the smooth, moist skin, its common name obtains due to its terrestrial habit.

Great Plains narrow-mouthed toads are a small (1.5 in), flat-bodied species, with a sharply pointed snout.

This toad is found in a wide range of habitats, but most frequently on moist ground or in leaf litter, and under rocks or fallen logs.

[3] Gastrophryne olivacea was once considered a subspecies of the eastern narrowmouth toad, G. carolinensis.