Pulgas Ridge Open Space Preserve, Public recreation area in San Mateo County, California.

Pulgas Ridge Open Space Preserve is a protected natural area in San Mateo County featuring an extensive network of trails through diverse forest and grassland habitats. The landscape transitions between dense evergreen forests, open oak woodlands, and seasonal meadows that create varied terrain for walking and exploration.

The site once contained the Hassler Health Farm, a tuberculosis sanatorium owned by San Francisco whose buildings were removed in 1985. The land was later converted into a protected preserve.

The preserve's trail names come from its own terrain and wildlife rather than from local figures: the Hassler Trail follows the route of the former Hassler Health Farm, and the Dusky-Footed Woodrat Trail is named for the woodrat that builds stick nests in the surrounding chaparral and oak woodland.

Visitors can access the preserve from dawn until 30 minutes after dusk on established trails with varying slopes and natural conditions. A designated section permits dogs to roam without leashes, making it suitable for visitors traveling with pets.

The preserve holds the source of Cordilleras Creek, which rises on its slopes. The 293 acres were bought in 1983 from the City of San Francisco, which had used the land for the Hassler Health Farm tuberculosis sanitarium. Old retaining walls and steps remain beside the Hassler Trail.