21 Squadron

21 Squadron or 21st Squadron may refer to:


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