John Quincy Marr (May 27, 1825 – June 1, 1861) was a Virginia militia company captain and the first Confederate soldier killed by a Union soldier in combat during the American Civil War. Marr was killed at the Battle of Fairfax Court House, Virginia on June 1, 1861. Previously one of Fauquier County's two delegates to the Virginia Secession Convention of 1861, Marr initially opposed his state's secession from the Union but ultimately supported secession, as did voters shortly before his fatal skirmish.