Hopper Mountain National Wildlife Refuge is located in Ventura County, in southern California. It is bordered by the Los Padres National Forest and the Sespe Condor Sanctuary to the north. The 2,471-acre refuge was established in 1974 to protect the endangered California condor, its habitat, and other wildlife resources. The refuge is in rugged, mountainous terrain. Primary habitats include annual grasslands, interspersed with oak and California black walnut groves, with chaparral on the steeper slopes, natural water springs and riparian habitat, and a freshwater marsh. The California black walnut community is considered to be a unique habitat in California, and is recorded in the State Natural Heritage Database. The refuge provides habitat for more than 130 species of birds, mammals, and reptiles, including the southwestern pond turtle--a California species of special concern--black bear, bobcat, mule deer, golden eagle, and California tree frog. More than 200 plant species have also been documented on the refuge. Hopper Mountain Refuge plays an integral part in the California Condor Recovery Program, providing foraging and roosting habitat for the bird. The refuge shares information about the Condor Recovery Program through an outreach program that extends to local, national and international publics. The refuge is closed to public use to protect habitat for the endangered California condor and to support ongoing efforts to reintroduce California condors to the wild. The road to the refuge runs through private lands, and the road itself is inaccessible to the general public. The U.S. Forest Service maintains two observation points in Los Padres National Forest.

The Hopper Mountain NWR is administered by the Hopper Mountain NWR Complex office in Ventura, CA, and is located in Ventura County, California, approximately 6 air miles north of the town of Fillmore. The refuge is closed to public use.