Alexander Keith McClung (14 June 1811 – 23 March 1855) was an attorney from Vicksburg, Mississippi, who briefly served as US chargé d'affaires to Bolivia in President Zachary Taylor's administration. An "inveterate Southern duelist" nicknamed "The Black Knight of the South", he killed as many as fourteen men in duels during his life. He was also a poet. James H. Street used him as the model for the character Keith Alexander in his novel Tap Roots (1942). McClung was born in Fauquier County, Virginia, and was the nephew of United States Chief Justice John Marshall. He served as lieutenant colonel of the 1st Mississippi Regiment during the Mexican–American War. He was widely despised for his ill manners, bad credit, gambling, and drunkenness. He committed suicide in the Eagle Hotel in Jackson, Mississippi. McClung was interred at Cedar Hill Cemetery in Vicksburg, Mississippi.