Franklin Mountains State Park is a state park in El Paso, Texas, United States. The park is named after the Franklin Mountains, a mountainous range that extends 23 mi (37 km) from El Paso to New Mexico. Its headquarters are located at an elevation of 5,426 feet (1,654 m) with the highest peak, North Franklin Mountain, reaching 7,192 feet (2,192 m). Covering 24,247.56 acres (9,813 ha), it is one of the largest urban parks in the U.S. lying completely within city limits. The park is owned and operated by the Texas Parks and Wildlife Department and is open year-round.

Native Americans and other travelers have used the natural resources in the Franklin Mountains when crossing the gap between the Franklin Mountains and the Juarez Mountains that is now Ciudad Juárez across the Rio Grande in Mexico and El Paso. Pictograms and mortar pits confirm a human presence in the mountains dating back more than 12,000 years.

The Franklin Mountains are most likely named after Benjamin Franklin Coons, who in 1849 purchased a ranch in what is now El Paso. At first known as Coons Ranch, by 1851 the settlement took on Coons' middle name and was called Franklin. Despite the town being officially named El Paso in 1852, the locals continued to call it Franklin throughout the 1850s.

The El Paso Tin Mining and Smelting Company operated a tin mine on the northeast slope of North Franklin Mountain from 1909 to 1915. While the mine had the distinction of being the only tin mine ever located in the U.S., it was an economic failure.

Efforts to grant protected status to the Franklin Mountains began as early as 1925. A real estate developer sought to build housing on the mountains and in 1979 he built a road up into them. A local organization known as the Wilderness Park Coalition was able to convince the Texas Legislature to protect the mountains in 1979. Despite this success the legislature, in the same bill, prohibited funding for the development, operation and maintenance of the park. The property was formally acquired in 1981. Changes to the legislation were made in 1985 when a plan for park development was established and the park was opened to the public in 1987.

The 1979 establishment allowed for the incorporation of the Castner Range on the east side of the park, though this did not happen due to the presence of unexploded ordnance. After decades pushing for its conservation, the Castner Range National Monument was established in 2023.

In May 2026, 1,054 acres (427 ha) to the east of the park were acquired. The acquisition provides access to the northeastern portion of the park and curbs urban encroachment.

The Franklin Mountains are 23 miles (37 km) long and 3 miles (4.8 km) wide and stretch from El Paso into New Mexico. The Franklins were formed due to crustal extension related to the Cenozoic Rio Grande rift. Although the present topography of the range and adjoining basins is controlled by extension during rifting in the last 10 million years, faults within the range also record deformation during the Laramide orogeny, between 85 and 45 million years ago.