The Peloncillo Mountains of Hidalgo County
, (Spanish language pelo, hair, pelon, hairless, bald; peloncillo, Little Baldy), is a major 35-mile (56 km) long mountain range of southwest New Mexico
's Hidalgo County, and also part of the New Mexico
Bootheel region. The range continues to the northwest into Arizona as the Peloncillo Mountains of Cochise County, Arizona. The extreme southwest corner of the range also lies in Arizona. It is a linear range bordering the linear San Bernardino Valley of southeast Cochise County, Arizona.
The Peloncillo Mountains lie in a region of southeast Arizona, southwest New Mexico, northeast Sonora, and extreme northwest Chihuahua called the Madrean Sky Islands. They are tall mountain ranges isolated by surrounding flatlands and valleys with sky islands of isolated fauna and flora. Various corridors exist between some ranges; others are mostly isolated. Some ranges are lower elevation, with a reduced variety of habitats.