Mount Umunhum, Summit and mountain in Santa Clara County, California, United States.

Mount Umunhum is a 3,489-foot (1,063 m) peak in the Santa Cruz Mountains, the fourth-highest in the range after Loma Prieta, Crystal Peak, and Mount Chual. Most of the mountain lies within the Sierra Azul Open Space Preserve. A road and a hiking and mountain biking trail to the summit opened on September 18, 2017; the summit has restrooms, interpretive displays, and a small parking lot.

The United States Air Force operated a Cold War radar station at the summit from 1962 until 1980, marked by a distinctive concrete tower. This military installation was part of the nation's air defense system during superpower tensions.

Mount Umunhum takes its name from the Ohlone language, in which it means "Resting Place of the Hummingbird". In 2017 the Midpeninsula Regional Open Space District granted an easement to the Amah Mutsun Tribal Band, descendants of the Ohlone, allowing them to build a garden and hold ceremonies on the mountaintop.

The 3.6-mile Mount Umunhum Trail climbs from the Bald Mountain parking area to the summit, where a small lot, restrooms and interpretive displays stand beside the Cube. The summit area around the tower was closed in 2018 for further cleanup, so check current access before setting out. The trail is a spur of the Bay Area Ridge Trail.

The northeast face of Mount Umunhum exposes the Coast Range Ophiolite, a piece of Middle Jurassic oceanic crust and mantle pushed onto land and largely turned to serpentinite. Geologists treat this outcrop as one of the Bay Area's best exposures of the formation, which also underlies the rocks of the Great Valley through central California.