The 9th Missouri Infantry Regiment (originally Clark's Missouri Infantry) was an infantry regiment that served in the Confederate States Army during the American Civil War. The unit was formed on November 16, 1862, and was originally commanded by Colonel John Bullock Clark Jr. At the Battle of Prairie Grove on December 7, 1862, the regiment was officially in Brigadier General John S. Roane's brigade, although it served with Brigadier General Mosby M. Parsons' brigade for most of the battle. After spending the summer of 1863 harassing Union Navy shipping on the Mississippi River, the regiment was reorganized, with elements of an Arkansas unit being replaced with the . After the reorganization, the regiment fought in the Battle of Pleasant Hill and the Battle of Jenkins' Ferry in April 1864.