The Arizona cotton rat is a large rodent of the southwestern United States and northwestern Mexico. It has dark brown-black fur above and silver or white fur below.
Its dorsal fur is coarse and brownish black, while its underside is silvery or whitish. The tail is dark above and lighter below, with sparse long hairs.
It is primarily associated with riparian corridors but also occurs in semidesert grassland. Live-trapping records show activity both by day and by night.
An extinction-risk assessment has not been added yet.