Hopper Mountain National Wildlife Refuge, Wildlife refuge in Ventura County, United States

Hopper Mountain National Wildlife Refuge covers 2,471 acres (about 1,000 hectares) in the Topatopa Mountains of Ventura County, bordered by Los Padres National Forest and the Sespe Condor Sanctuary to the north. Its terrain is rugged and mountainous, with annual grasslands interspersed with oak and California black walnut groves, chaparral on the steeper slopes, natural springs, riparian habitat and a freshwater marsh.

The refuge was established in 1974 by the United States Fish and Wildlife Service to protect the California condor population and its habitat. This protected area became a crucial effort in rescuing this endangered species from extinction.

The refuge carries out an outreach programme on the California Condor Recovery Program for local, national and international audiences. Its role in the recovery effort is to supply foraging and roosting ground for free-flying condors, 68 of which the US Fish & Wildlife Service managed in Southern California as of July 2014.

The refuge is closed to public use, and the road to it runs through private land and is inaccessible to the general public. The U.S. Forest Service maintains two observation points in Los Padres National Forest for viewing the area.

The refuge's California black walnut community is listed in the State Natural Heritage Database as a rare plant formation. The refuge also holds a freshwater marsh and natural springs, habitats not mentioned in its federal founding purpose.