398th

398th may refer to:


 * 398th Air Expeditionary Group, provisional United States Air Force unit assigned to the United States Air Forces in Europe
 * 398th Bombardment Squadron, inactive United States Air Force unit last assigned with the 92d Operations Group at Fairchild Air Force Base, Washington
 * 398th Fighter-Interceptor Squadron, inactive United States Air Force unit, last assigned to the Air Defense Command stationed at Hamilton AFB, California