The Battle of La Mesa was the final battle of the California Campaign during the Mexican–American War, occurring on January 9, 1847, in present-day Vernon, California, the day after the Battle of Rio San Gabriel. The battle was a victory for the United States Army under Commodore Robert F. Stockton and General Stephen Watts Kearny.

The battle was the last armed resistance to the American conquest of California, and General José María Flores returned to Mexico afterward. Three days after the battle, on January 12, the last significant group of residents surrendered to U.S. forces. The conquest and annexation of Alta California was settled with the signing of the Treaty of Cahuenga by U.S. Army Lieutenant-Colonel John C. Frémont and Mexican General Andrés Pico on January 13, 1847.