The 4th Pennsylvania Reserve Regiment was a Union Army regiment from Pennsylvania which was active from 17 July 1861 to 8 June 1864 during the American Civil War. Raised at Harrisburg with five Philadelphia companies, and one company each from Montgomery, Lycoming, Monroe, Susquehanna, and Chester Counties, the regiment served with the Army of the Potomac starting with the Peninsula Campaign and ending with the Battle of Fredericksburg, after which the regiment was transferred to Washington DC. It was dispatched to West Virginia in 1864 and lost its colonel, Richard H. Woodworth, at the Battle of Cloyd's Mountain. The depleted regiment was mustered out at Philadelphia on 15 June 1864. The regiment lost 139 men during the war, including 2 officers and 76 enlisted men killed and 1 officer and 60 enlisted men dead from disease.