505th

505th may refer to:


 * 505th Bombardment Group, inactive United States Air Force unit
 * 505th Bombardment Squadron, part of the 319th Air Refueling Wing at Grand Forks Air Force Base, North Dakota
 * 505th Brigade, Brigade of the Army of the Republic of Bosnia and Herzegovina
 * 505th Command and Control Wing, organized under the USAF Warfare Center
 * 505th Fighter Squadron or 138th Fighter Squadron, squadron of the United States Air Force
 * 505th Infantry Regiment (United States) (505th PIR), one of four infantry regiments of the 82nd Airborne Division of the United States Army