406th

406th may refer to:


 * 406th Air Expeditionary Group, the operational flying component of the 406th Air Expeditionary Wing
 * 406th Air Expeditionary Wing, a provisional unit assigned to the United States Air Forces in Europe
 * 406th Bombardment Squadron or 906th Air Refueling Squadron (906 ARS), part of the 375th Air Mobility Wing at Scott Air Force Base, Illinois
 * 406th Support Brigade (United States), support brigade of the United States Army