121 Squadron may refer to:
No. 121 Squadron RAF, United Kingdom 121 Squadron, Republic of Singapore Air Force 121 Squadron SAAF, South Africa 121st Fighter Squadron, United States Air Force 121st Observation Squadron, United States Army Air Forces VAW-121, United States Navy VF-121, United States Navy VMFA-121, United States Marine Corps
See also 121st Weather Flight 121st Air Refueling Wing