California Coastal National Monument, Protected offshore ecosystem along California coast, US.

The California Coastal National Monument covers every islet, reef and rock outcropping above the mean high-water line within 12 nautical miles of California's 840-mile (1,350 km) coastline, at least 20,000 features averaging only 3 m². The first onshore unit, Point Arena-Stornetta, added 1,665 acres of Garcia River estuary in 2014; six onshore units now total 7,924 acres.

The monument was established in January 2000 by President Bill Clinton using the Antiquities Act of 1906 to protect marine habitats. This designation marked an important conservation effort for the ecological resources along the California coast.

The monument's cultural record is tied to the Cotoni people, whose ancestral sites lie within the Cotoni-Coast Dairies unit in Santa Cruz County. The Bureau of Land Management works with the Amah Mutsun Tribal Band to protect four registered ancestral archaeological sites there. The unit also preserves the remains of a farm and ranching operation run for most of the 20th century by descendants of two Swiss families.

Visitors can access designated areas at Trinidad Head, Point Arena, Fort Bragg-Mendocino, and Pigeon Point Lighthouse for wildlife viewing and coastal exploration. The best times for observation depend on seasonal migration patterns and weather conditions throughout the year.

The smallest designated Wilderness Area in the United States lies within the monument: a chain of islets south of Cape Mendocino totalling about 2 hectares, protected since 2006 as Rocks and Islands Wilderness. The monument's rocks average only 3 square metres each, and no visitor centre exists anywhere in it.