404th

404th may refer to:


 * 404th Air Expeditionary Group, provisional United States Air Force unit assigned to the United States Air Forces in Europe
 * 404th Bombardment Squadron or 904th Air Refueling Squadron, inactive United States Air Force unit
 * 404th Fighter Group, inactive United States Army Air Force unit
 * 404th Fighter Squadron or 186th Fighter Squadron flies the F-15C Eagle
 * 404th Maneuver Enhancement Brigade, maneuver enhancement brigade of the United States Army National Guard in Illinois