The Middle Military Division was an organization of the Union Army during the American Civil War, responsible for operations around the Shenandoah Valley of Virginia and the Valley Campaigns of 1864.
In the summer of 1864, Confederate General Jubal Early's army had defeated several Union armies, had advanced close to Washington, D.C., and continued to operate in the Shenandoah Valley into August. Faced with this continued threat, the Union high command created the Middle Military Division and ordered the cavalry commander of the Army of the Potomac, Major General Phillip Sheridan, to command it. The Military Division (an entity that controlled multiple military departments within the Union Army) was established on August 7, 1864. It comprised the geographic and military assets of the Departments of the Susquehanna, Washington, West Virginia, and the Middle Department. On December 1, 1864, the Department of the Susquehanna within the military division changed its name to the Department of Pennsylvania.
The operational field forces of the division were collectively known as the Army of the Shenandoah. Philip Sheridan commanded both the military division and the army from August 7 to October 18, 1864.