The 4th Pennsylvania Infantry Regiment, officially known as the 4th Regiment, Pennsylvania Volunteer Infantry, was an infantry regiment of the Union Army in the American Civil War. Formed mostly from a militia unit in Norristown in southeastern Pennsylvania, the regiment enlisted at the beginning of the American Civil War in April 1861 for a three-month period of service under the command of Colonel John F. Hartranft. Logistical difficulties bedeviled the regiment, which served as part of the garrison of Washington, D.C. until late June, when it was sent into northern Virginia to join the army of Brigadier General Irvin McDowell. The regiment suffered its only combat casualties in a picket action on June 30 and was sent back to be mustered out on the eve of the First Battle of Bull Run owi