Robert Patterson (January 20, 1792 – August 7, 1881) was a United States major general during the Mexican-American War and the American Civil War. During the onset of the latter, he commanded a brief engagement with Colonel Thomas J. Jackson on July 2, 1861, at the Battle of Hoke's Run and produced an early Union victory. His inability to contain a smaller Confederate army under General Joseph E. Johnston within the Shenandoah Valley was a proximate cause for the Union Army's defeat at the First Battle of Bull Run, but among Johnston's stated reasons for avoiding pursuit of the shattered Union Army as it fled in retreat to Washington, the size, integrity and mobility of Patterson's Army is prominent. Shortly after First Bull Run, the three-month term of the volunteers who comprised a majority of his army expired, Patterson was honorably discharged with them, and his active military career ended. Patterson was born in Cappagh, County Tyrone, Ireland. His family was banished from Ireland due to his father's involvement as an insurrectionist. In 1799 he emigrated to the United States, where he eventually became involved in banking at a young age.