El Sereno Open Space, Protected area in Santa Clara County, US

El Sereno Open Space is a park unit of the Midpeninsula Regional Open Space District on the peak and slopes of 2,580-foot El Sereno mountain in the Santa Cruz Mountains, Santa Clara County. The San Andreas Fault runs in the valley immediately south of the mountain, and the Berrocal fault zone runs under its northern slope. The northern slope forms the headwaters of San Tomas Aquino Creek.

The land was acquired in 1975 when the Midpeninsula Regional Open Space District purchased it to protect the natural landscape near Los Gatos. This purchase was a significant milestone in regional efforts to conserve open spaces throughout the area.

The city of Monte Sereno takes its name from El Sereno mountain, and part of the city is built on the mountain's foothills. El Sereno is paired with El Sombroso on either side of Los Gatos. Signs at the preserve entrance warn visitors that the mountain is cougar habitat.

Limited parking is available at the end of Montevina Road, where the Montevina Ridge Trail begins and connects to Bohlman Road and the Aquinas Trail. The Aquinas Trail links to Sheldon Road, the Serenity Trail and the Loma Vista Trail; the Serenity Trail ends at a power pole above Lexington Reservoir, and the Loma Vista Trail reaches Overlook Drive. Permit parking is available at the westernmost Overlook Drive spot for the Overlook Trail.

Two fault zones run beneath the terrain of this protected area, shaping its geological character. The northern slope of the mountain is also where San Tomas Aquino Creek originates, making the site hydrologically significant.