The 3rd Missouri Infantry Regiment served in the Confederate States Army during the American Civil War. The infantry regiment was officially mustered into service on January 17, 1862. It fought at the Battle of Pea Ridge in Arkansas in March before being transferred across the Mississippi River. While stationed at Corinth, Mississippi, the regiment played a minor role in the Battle of Farmington before the evacuation of the town. In September, the unit saw light action at the Battle of Iuka before being heavily engaged during the Second Battle of Corinth as the Confederates attempted to retake the town in October. In early 1863, the regiment was transferred to Grand Gulf, Mississippi, in order to strengthen the defenses of the Mississippi River at that point. At the Battle of Grand Gulf on April 29, the unit helped repulse a Union Navy attack against the Confederate defensive works. After elements of the Union Army of the Tennessee landed below Grand Gulf, the regiment fought in a delaying action at the Battle of Port Gibson on May 1.