The 393d Bombardment Group is a disbanded United States Air Force unit. It was part of Second Air Force, and last stationed at Sioux City Army Air Base, Iowa, where it was inactivated on 1 April 1944. During World War II the group was a Boeing B-17 Flying Fortress Operational Training Unit, and later a Replacement Training Unit. It was inactivated in April 1944 in a general reorganization of Army Air Forces training units.