California oak woodland is a plant community found throughout the California chaparral and woodlands ecoregion of California in the United States and northwestern Baja California in Mexico. Oak woodland is widespread at lower elevations in coastal California; in interior valleys of the Coast Ranges, Transverse Ranges and Peninsular Ranges; and in a ring around the California Central Valley grasslands. The dominant trees are oaks, interspersed with other broadleaf and coniferous trees, with an understory of grasses, herbs, geophytes, and California native plants.

Oak savannas occur where the oaks are more widely spaced due a combination of lack of available moisture, and low-intensity frequent fires.

The oak woodlands of Southern California and coastal Northern California are dominated by coast live oak (Quercus agrifolia), but also include valley oak (Q. lobata), California black oak (Q. kelloggii), canyon live oak (Q. chrysolepis), and other California oaks. The foothill oak woodlands around the Central Valley are dominated by blue oak (Q. douglasii) and gray pine (Pinus sabiniana).

The headwaters area of Yulupa Creek in Annadel State Park is cited as one of the best examples of California oak woodlands. Much of this woodland is a relatively pristine ecosystem with considerable biodiversity. An unusual characteristic of this Annadel forest is the high content of undisturbed prehistoric bunch grass understory, testifying to the absence of historic grazing or other agriculture.^{[citation needed]}

The Morro Bay watershed, located in Central California, is an example of a coast live oak ecosystem. This sub-category of California oak woodland consists primarily of coast wild oak and are predominantly found in coastal regions, but can extend to foothill ecosystems.

The composition and characteristics of California oak woodlands varies across the state, but are defined by three main oak species throughout coastal regions: coastal live oak, Englemann oak, and Oregon white oak. The concentration of each of these oak species correlates with the location of the woodland throughout California.

In the Sierra Nevada range, oak woodland is found on western slopes at elevations of 500 to 3,000 feet (150 to 910 m) in the northern part of the range, 800 to 4,000 feet (240 to 1,220 m) in the central part, and 1,250 to 5,000 feet (380 to 1,520 m) in the southern part. Annual precipitation in the oak woodland range is 15 to 40 inches (0.38 to 1.02 m), with little precipitation in the summer. Growing season is 6–10 months. Temperatures range 75 to 96 °F (24 to 36 °C) in the summer, and 29 to 42 °F (−2 to 6 °C) in winter. The woodlands in the Sierra are characterized by a dominant overstory of Foothill Pine (Pinus sabiniana), Blue Oak (Quercus douglasii), Interior Live Oak (Quercus chrysolepis), California Black Oak (Quercus kelloggii), California Buckeye (Aesculus californica), and understory plants including Ceanothus spp., Toyon (Heteromeles arbutifolia), Dogwood (Cornus spp.), and Redbud (Cercis occidentalis). It is often found on north facing slopes there is more moisture in the soils from protection from the sun (slope effect).

In southern and central areas, the predominant oak species is coastal live oak which grow on coastal valleys and foothills. In drier regions within this range, coastal wild oak is associated with foothill pine, valley oak and blue oak; whereas wetter areas are defined by tanoak, canyon live oak and California bay. Coastal live oak woodland found in Southern California is associated with valley oak similar to drier northern sites, but also sees interior live oak, Coulter pine and California black walnut.^{[citation needed]}