Southern Arizona is a region of the United States. It is the southernmost portion of the 48th state, Arizona. Southern Arizona's boundaries are not well defined, but certainly include all of present-day Cochise County, Pima County, and Santa Cruz County.

The principal cities of the area include Tucson, Sierra Vista, Nogales, and Douglas. There are no other cities in the area with more than 10,000 persons. A large Native American reservation, the Tohono O'odham nation, lies in the western desert portions of the area.