Blue Oak Ranch Reserve, Ecological reserve in Santa Clara County, California.

Blue Oak Ranch Reserve is a 3,260-acre (13.2 km2) ecological reserve and biological field station of the University of California Natural Reserve System, in the Diablo Range northwest of Mount Hamilton at about 1,500 ft (460 m) elevation. Its plant communities range from valley oak, black oak and coast live oak woodlands to chamise chaparral, Diablan sage scrub, riparian forest and native perennial grassland.

The land was originally part of Rancho Cañada de Pala during the Mexican period before being transferred to the University of California through the Blue Oak Ranch Trust in 2007. This transfer established its current role as a research-focused protected area.

The reserve's name comes from the blue oaks of its woodlands, and the land was once part of Rancho Cañada de Pala. Today it serves as a biological field station of the University of California Natural Reserve System, where researchers and educational groups stay overnight by permission only.

Overnight accommodations for academic researchers and educational groups are available by permission only; there are no public day-use facilities. The reserve lies in the Diablo Range northwest of Mount Hamilton, at about 1,500 ft (460 m) elevation, and is reached from Santa Clara County roads. Arrange access with the reserve before travelling.

The reserve's ponds and streams hold California newts, western pond turtles and California tiger salamanders, while introduced sunfish, largemouth bass and mosquitofish share the same water. The 3,260-acre site was donated to the University of California on December 1, 2007, by the Blue Oak Ranch Trust, an anonymous benefactor.