The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central California, United States. They form a ridge along the San Francisco Peninsula, south of San Francisco, separating the Pacific Ocean from San Francisco Bay and the Santa Clara Valley, and continuing south, bordering Monterey Bay and ending at the Salinas Valley. The range passes through San Mateo, Santa Clara and Santa Cruz counties, with the Pajaro River forming the southern boundary.