The Guadalupe Mountains are a mountain range located in West Texas and southeastern New Mexico. The range includes the highest summit in Texas, Guadalupe Peak, 8,751 feet (2,667 m), and the signature peak of West Texas, El Capitan, both of which are located within Guadalupe Mountains National Park.

The Guadalupe Mountains are bordered on the east and north by the Pecos River valley and Llano Estacado, commonly called the South Plains. To the south rises the Delaware Mountains and to the west rises the Sacramento Mountains.

The mountain range extends north-northwest and northeast from Guadalupe Peak in Texas into New Mexico.

The Guadalupe Mountains reach their highest point at Guadalupe Peak, the highest point in Texas, with an elevation of 8,751 feet (2,667 m).

The northeastern extension ends about 10 miles (16 km) southwest of Carlsbad and Carlsbad Caverns National Park. The southwest tip ends with El Capitan about 90 miles (140 km) east of El Paso.

The mountains rise more than 3,000 feet (910 m) above the arid floor of the Chihuahuan Desert.

Much of the range is built from the ancient Capitán Reef that formed at the margins of a shallow sea during the Permian period.

The Guadalupian epoch of the Permian period is named for these mountains, and the Capitanian age within this epoch is named for the Capitan reef.

Since the range is built up almost entirely of limestone, upland areas have little or no surface water.

The Delaware Basin is a geologic depositional and structural basin in West Texas and southern New Mexico, famous for holding large oil fields and for a fossilized reef exposed at the surface. Guadalupe Mountains National Park and Carlsbad Caverns National Park protect part of the basin. It is part of the larger Permian Basin, itself contained within the Mid-Continent oil province.

The Delaware, Midland and Marfa basins were foreland basins created when the Ouachita Mountains were uplifted as the southern continent Gondwana collided with Laurasia, forming the supercontinent Pangea in the Late Carboniferous period (Pennsylvanian) about 300 mya.

The Ouachita Mountains formed a rainshadow over the basins, and a warm shallow sea flooded them and the surrounding area. On the other side of the equator, the Ancestral Rocky Mountains formed a large mountainous island.

Uplift associated with the Laramide orogeny in the late Mesozoic and early Cenozoic created a major fault along which the Guadalupe Mountains were thrusted upwards into existence.

The Guadalupe Mountains forms the tilted up thrown part of the mountain system and the Salt Flat Bolson forms the downfallen block. Capitan Reef limestone was exposed above the surface with the 1000-foot-high (300 m) El Capitan being its most prominent feature.

Other large outcrops compose the Apache Mountains and Glass Mountains to the south.