The Fifteenth United States Army, commonly known as Fifteenth Army, was a field army of the United States in the European Theater of World War II. It was the last United States field army to see service in northwestern Europe during the war and was commanded by General George S. Patton until his death in December 1945. The Fifteenth Army served two separate missions while assigned to the area. During the later stages of the war its mission was the training and rehabilitation of units and acting as a defensive line against counterattacks. After World War II its mission was to carry out occupation duties and to gather historical information related to the European Theater of Operations. Fifteenth Army was inactivated at Bad Nauheim, Germany, in 1946.

George Smith Patton Jr. was a general in the United States Army who commanded the Seventh Army in the Mediterranean Theater of World War II, and the Third Army in France and Germany after the Allied invasion of Normandy in June 1944.