Telegraph Peak, Mountain summit in San Gabriel Mountains, California, United States.

Telegraph Peak is a peak of the San Gabriel Mountains in San Bernardino County, California, reaching 8,989 feet (2,740 m). It is the highest point in the Cucamonga Wilderness of the San Bernardino National Forest. Most of the bedrock, including the summit, is cataclastic gneiss, while granodiorite underlies much of the southern portion.

The mountain received its current name in the 1890s, replacing the former designation Heliograph Hill, which referred to mirror-based communication methods. This name change reflects how communication technology evolved in the region during that period.

Telegraph Peak is the highest point in the Cucamonga Wilderness of the San Bernardino National Forest, and hikers often link it with nearby Mount San Antonio, about 5.4 km away, and other summits of the San Gabriel range. The peak lies within the San Gabriel Mountains National Monument, and the surrounding slopes are covered by woodland typical of a Mediterranean climate.

Telegraph Peak lies in the Cucamonga Wilderness of the San Bernardino National Forest, and the summit is the highest point in that wilderness at 8,989 feet. The peak sits about 5.4 km from Mount San Antonio and roughly 17 km from Rancho Cucamonga. Approach from the trailheads along the San Gabriel Mountains crest, where the terrain is steep and the bedrock is mostly cataclastic gneiss.

Telegraph Peak is the highest point in the Cucamonga Wilderness of the San Bernardino National Forest, reaching 8,989 feet. Its summit bedrock is cataclastic gneiss, while granodiorite underlies much of the southern portion. The peak stands about 5.4 km from Mount San Antonio, the taller summit to its northwest.