The California Republic was a short-lived, unrecognized state that, for a few weeks in 1846, militarily controlled the area to the north of the San Francisco Bay in the present-day state of California.

In June 1846, a number of American immigrants in Alta California rebelled against the Mexican department’s government. The immigrants had not been allowed to buy or rent land and had been threatened with expulsion from California because they had entered without official permission. Mexican officials were concerned about a coming war with the United States coupled with the growing influx of Americans into California. The rebellion was soon overtaken by the beginning of the Mexican–American War.