501st

501st may refer to:

Fiction

 * 501st Legion (Star Wars), fictional legion within the Star Wars expanded universe
 * 501st Joint Fighter Wing "Strike Witches", a fictional air force unit in the anime series Strike Witches

Military

 * 501st Heavy Panzer Battalion
 * 501st Squadron (disambiguation), several units

United States

 * 501st Combat Support Wing
 * 501st Infantry Regiment (United States)
 * 501st Military Intelligence Battalion (United States)
 * 501st Military Intelligence Brigade (United States)
 * 501st Sustainment Brigade (United States)
 * 501st Aircraft Control and Warning Battalion, a forerunner of the 603rd Air Control Squadron
 * 501st Reconnaissance Battalion, a former unit of the 15th Cavalry Regiment
 * 501st Bombardment Group, a forerunner of the 501st Combat Support Wing
 * 501st Tactical Missile Wing, a former unit of the United States Third Air Force

Other uses

 * 501st Legion, a fan-based organization dedicated to screen-accurate replicas of villain costumes from the Star Wars universe