Mount Thayer, Mountain summit in Santa Clara County, California, US.

Mount Thayer is a mountain in the Santa Cruz range in Santa Clara County, California, reaching 3,502 feet (1,067 m). Its summit lies within the abandoned Almaden Air Force Station, 1.5 miles northwest of Mount Umunhum, and holds a derelict building surrounded by telephone poles.

The mountain was home to Almaden Air Force Station during the Cold War when it served as a military outpost. The facility was decommissioned over time, leaving behind the ruins visible today.

The summit lies within the abandoned Almaden Air Force Station, a Cold War-era radar post of the U.S. military. Telephone poles and a derelict building remain at the top, and the site is off limits to the public. The station's name comes from the nearby New Almaden quicksilver mines.

The summit is closed to public access with no maintained pathways to reach the top. Visitors can view the mountain from the surrounding areas of Sierra Azul Open Space Preserve.

Mount Thayer's summit lies within a section of the abandoned Almaden Air Force Station, 1.5 miles northwest of Mount Umunhum. A derelict building ringed by telephone poles stands at the top, and the mountain and surrounding property are off limits to the public.