The California genocide was the killing of thousands of indigenous peoples of California by United States government agents and private citizens in the 19th century. It began following the American Conquest of California from Mexico, and the influx of settlers due to the California Gold Rush, which accelerated the decline of the indigenous population of California. Between 1846 and 1873, it is estimated that non-Natives killed between 9,492 and 16,094 California Natives. Hundreds to thousands were additionally starved or worked to death. Acts of enslavement, kidnapping, rape, child separation and displacement were widespread. These acts were encouraged, tolerated, and carried out by state authorities and militias.

The 1925 book Handbook of the Indians of California estimated that the indigenous population of California decreased from perhaps as many as 150,000 in 1848 to 30,000 in 1870 and fell further to 16,000 in 1900. The decline was caused by disease, low birth rates, starvation, killings, and massacres. California Natives, particularly during the Gold Rush, were targeted in killings. Between 10,000 and 27,000 were also taken as forced labor by settlers. The state of California used its institutions to favor white settlers' rights over indigenous rights, dispossessing natives.