The California Battalion (also called the first California Volunteer Militia and U.S. Mounted Rifles) was formed during the Mexican–American War (1846–1848) in present-day California, United States. It was led by U.S. Army Brevet Lieutenant Colonel John C. Frémont and composed of his cartographers, scouts and hunters and the California Volunteer Militia formed after the Bear Flag Revolt. The battalion's formation was officially authorized by Commodore Robert F. Stockton, commanding officer of the U.S. Navy Pacific Squadron.