Ruby, ghost town in Santa Cruz County, Arizona

Ruby is a ghost town at the base of Montana Peak in the Pajarita Wilderness of Santa Cruz County, Arizona, about 25 miles west of Rio Rico and 7 miles north of the Mexican border. Roughly 25 buildings remain, among them homes, a jail and a school, along with a playground, mining machinery and abandoned mine shafts. A long single-story building with pale weathered walls and a dark low-pitched roof stands on a shelf cut into the hillside against a grey tailings pile.

Ruby began in 1877 as Montana Camp, a mining settlement whose Montana mine produced mostly gold and silver until 1912, with a population never exceeding 50. On 11 April 1912, store owner Julius Andrews opened the post office and named it Ruby after his wife, Lille B. Ruby Andrews. The Eagle-Picher Lead Company operated the mine in the late 1920s and 1930s, when Ruby peaked at about 1,200 residents; the mine closed in 1940 and the town was abandoned by the end of 1941.

Julius Andrews, owner of the mining camp's general store, opened the post office on 11 April 1912 and named it Ruby after his wife, Lille B. Ruby Andrews; the camp then took the name. The schoolhouse and jail are among the roughly 25 surviving buildings, and the school's chalkboard, armchair and bookcase remain in place.

Ruby is on private property and currently has no public access; public tours ran from 1994 until 2024 and have ended. The site lies near the base of Montana Peak in the Pajarita Wilderness, about 25 miles west of Rio Rico and 7 miles north of the Mexico–United States border.

Ruby's notoriety comes from the Ruby Murders of 1920–1922, three double homicides that triggered the largest manhunt in the history of the Southwestern United States. An airplane was used in the pursuit, the first ever in an Arizona manhunt. The case drew attention to this remote mining camp near the Mexico border.