401 Squadron or 401st Squadron may refer to:
401 Tactical Fighter Squadron, Canada 401 Squadron (Portugal) 401st Tactical Airlift Squadron (JASDF), Japan 401st Aero Squadron, Air Service, United States Army, see list of American aero squadrons 401st Bombardment Squadron, United States Air Force 401st Fighter Squadron, United States Air Force VMFT-401, United States Marine Corps