Anza-Borrego Desert State Park, State park in San Diego County, California, United States

Anza-Borrego Desert State Park is a California state park in eastern San Diego County that reaches into Imperial and Riverside counties. It covers 650,000 acres of the Colorado Desert, with mountains such as the Vallecito Mountains to the south and the Santa Rosa Mountains to the north. The park includes Borrego Palm Canyon, where California fan palms grow on rocky slopes, and broad arid flats scattered with pale rocks and scrub.

Anza-Borrego Desert State Park was created in 1932. It is named after Juan Bautista de Anza, the 18th-century Spanish explorer, and borrego, the Spanish word for sheep. The park covers 650,000 acres, including one-fifth of San Diego County, and reaches into Imperial and Riverside counties. It surrounds Borrego Springs, home to the park headquarters, and Shelter Valley.

The park's name combines Juan Bautista de Anza, the 18th-century Spanish explorer who crossed the desert here, with borrego, Spanish for sheep, referring to the bighorn sheep of the rocky slopes. The park headquarters and main visitor area sit at Borrego Palm Canyon, named for the California fan palms that grow there.

Access from the Coachella Valley side is via County Route S22 and State Route 78; from the west, County Route S2 and State Route 78; SR-79 crosses the Laguna Mountains past Cuyamaca Rancho State Park. These highways climb to about 2,400 ft (730 m) before descending roughly 2,000 ft (610 m) into Borrego Valley. The park holds 500 mi (800 km) of dirt roads, 110 mi (180 km) of hiking trails, four developed and eight primitive campgrounds, and Wi-Fi at the visitor center.

Recognition as an International Dark Sky Park reflects the unusually dark night skies, which show constellations and the Milky Way without interference from settlement lights. Astronomy events take place regularly and use the clear desert conditions for sky observation.