1st Missouri Light Artillery Regiment was a artillery unit from Missouri that served in the Union Army during the American Civil War. The unit began its service as the 1st Missouri Infantry Regiment, but converted to an artillery regiment in September 1861 and was brought up to a strength of 12 companies. Thereafter, each company served as an individual artillery battery, often separated from the other companies in the regiment. The individual batteries served in many actions in the Western Theater of the American Civil War and several batteries served together at key battles such as Fort Donelson, Shiloh, Corinth, Prairie Grove, and Vicksburg.