Angeles National Forest, National forest in Los Angeles County, California, US

The Angeles National Forest covers 700,176 acres (about 2,833 km²) of the San Gabriel and Sierra Pelona mountains, mostly in Los Angeles County, with a small eastern extension into San Bernardino County near Mount San Antonio and a sliver in Ventura County near Lake Piru. Headquarters are in Arcadia. The Pacific Crest Trail crosses the forest, and elevations run from roughly 1,200 to 10,064 feet at Mount San Antonio. Its five designated wilderness areas include Cucamonga and Sheep Mountain, which partly extend into San Bernardino National Forest.

The San Gabriel Forest Reserve was set aside on 20 December 1892, the San Bernardino Reserve on 25 February 1893 and the Santa Barbara Reserve on 22 December 1903; all became national forests on 4 March 1907. On 1 July 1908 they were combined, with the whole San Bernardino forest and parts of the San Gabriel and Santa Barbara forests forming the new Angeles National Forest. On 30 September 1925 parts of it and of Cleveland National Forest were separated to re-establish San Bernardino National Forest. The forest is California Historical Landmark 717, as the state's first national forest.

The forest's name comes from the San Gabriel Mountains' early Spanish mission links; the Portolá expedition passed the neighbouring valleys in 1769, and the San Gabriel Archangel mission was founded in 1771. Visitors can still see place names such as Tujunga and San Francisquito, and the ruins of the St. Francis Dam in San Francisquito Canyon, now a national memorial.

A National Forest Adventure Pass is required for parking and can be purchased at several visitor centers with ranger stations. Elevation varies widely, so visitors should prepare for rapid weather changes.

Five designated wilderness areas provide protection for black bears, mountain lions, and bobcats. Archaeological finds show that people have used this area for more than 7,600 years.