21 Squadron

21 Squadron or 21st Squadron may refer to:


 * No. 21 Squadron RAAF, a unit of the Australian Royal Air Force
 * No. 21 Squadron SAAF, a unit of the South African Air Force
 * No. 21 Squadron RAF, a unit of the United Kingdom Royal Air Force
 * 21st Aeromedical Evacuation Squadron (United States), a unit of the United States Air Force
 * 21st Airlift Squadron (United States), a unit of the United States Air Force
 * 21st Bombardment Squadron (United States), an inactive unit of the United States Air Force
 * 21st Fighter Squadron (United States), a unit of the United States Air Force
 * 21st Operational Weather Squadron (United States), a unit of the United States Air Force
 * 21st Photographic Reconnaissance Squadron, an inactive unit of the United States Air Force
 * 21st Pursuit Squadron (United States), an inactive unit of the United States Air Force
 * 21st Space Operations Squadron (United States), a unit of the United States Air Force
 * 21st Special Operations Squadron (United States), a unit of the United States Air Force
 * 21st Tactical Air Support Squadron, an inactive unit of the United States Air Force