Green Valley is a census-designated place (CDP) in Pima County, Arizona, United States. The population was 23,765 at the 2010 census.
Green Valley is located along the western side of the Santa Cruz River at 31°51′N 111°0′W (31.8556, -111.0001). Continental is to the east of Green Valley, on the other side of the river.
According to the United States Census Bureau, the CDP has a total area of 26.3 square miles (68.0 km²), of which, 26.2 square miles (68.0 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.08%) is water.
Green Valley is twenty miles (32 km) south of Tucson and 40 miles (64 km) north of Nogales, Sonora, Mexico. Surrounded by copper mines, and near the cycling, hiking and birding areas of the Santa Rita Mountains, Green Valley is an unincorporated retirement community composed of 59 Homeowner Associations.
The largest of the mines are the Sierrita Mine owned by Freeport-McMoRan and the Mission Mine of ASARCO. Compared to other mines in Arizona the two mines are large; Sierrita is low-grade.
Green Valley has a borderline hot semi-arid/hot desert climate (Köppen BSh/BWh) with three seasons: a warm to mild winter with chilly nights from October through March; a hot, extremely dry summer season from April to late June; and a hot, relatively humid monsoon season from July through September. Outside monsoon season, rainfall is uniformly scarce, having exceeded 4.0 inches or 100 millimetres only in October 2000 amongst other months.