El Pinacate and Gran Desierto de Altar Biosphere Reserve (Spanish: Reserva de la Biosfera El Pinacate y Gran Desierto de Altar) is a biosphere reserve and UNESCO World Heritage Site managed by the federal government of Mexico, specifically by Secretariat of the Environment and Natural Resources, in collaboration with the state governments of Sonora and the Tohono O'odham.

It is in the Sonoran Desert in northwest Mexico, east of the Gulf of California, in the eastern part of the Gran Desierto de Altar, just south of the border with Arizona, United States and north of the city of Puerto Peñasco. It is one of the most significant visible landforms in North America seen from space. A volcanic system known as Santa Clara is the main part of the landscape, including three peaks: Pinacate, Carnegie and Medio. It is a sister park to Organ Pipe Cactus National Monument in Arizona. Its wildlife is threatened by the militarization of the Mexico–United States border and the construction of the Mexico–United States border wall.

In the area there are over 540 species of plants, 40 species of mammals, 200 of birds, 40 of reptiles, amphibians and freshwater fishes. There are threatened endemic species as Sonoran pronghorn, bighorn sheep, gila monster and desert tortoise.

The biosphere reserve covers an area of 2,695.05 square kilometres (1,040.56 sq mi), making up about half of the World Heritage site. The extent of the World Heritage site is 7,146 km², greater than that of the states of Aguascalientes, Colima, Morelos and Tlaxcala separated.