The western harvest mouse is a small neotomine mouse native to most of the western United States. Many authorities consider the endangered salt marsh harvest mouse to be a subspecies, but the two are now usually treated separately.

The Neotominae are a subfamily of the family Cricetidae. They consist of four tribes, 16 genera, and many species of New World rats and mice, predominantly found in North America. Among them are the well-known deer mice, white-footed mice, packrats, and grasshopper mice.