The 51st United States Colored Infantry Regiment was a U.S.C.T. infantry regiment in the Union Army during the American Civil War. It was organized from the 1st Mississippi Infantry March 11, 1864. It served in various posts in the Department of the Gulf and fought in the Battle of Fort Blakely as part of the Pensacola Column and the assault and capture of Fort Blakely April 9. The Siege of Fort Blakely took place from April 1–9, 1865. The 51st was mustered out on June 16, 1866.