Thornewood Open Space Preserve is a small regional park located in the Santa Cruz Mountains in San Mateo County.

The park lies in the San Francisco Bay Area and is operated by the Midpeninsula Regional Open Space District.

This trail offers brief views of the southern San Francisco Bay, Palo Alto (including Stanford University's Hoover Tower) and surrounding cities, and the Diablo Range.

[3] Second-growth redwood trees grow in portions of Thornewood Open Space Preserve, especially by the lake.

In 2005, the district approved a $1.2 million plan to eradicate a newly-discovered invasive strain of slender false brome that was displacing native plants.