321st Missile Squadron, US Air Force missile squadron at F.E. Warren AFB, Wyoming, United States

The 321st Missile Squadron is a United States Air Force unit assigned to the 90th Operations Group at Francis E. Warren Air Force Base, Wyoming. It is equipped with the LGM-30G Minuteman III intercontinental ballistic missile and is one of four Minuteman squadrons of the 90th Wing. Its mission is to operate safe and secure nuclear weapons, maintain mission-ready facilities, and on order destroy OPLAN-assigned targets.

The unit began operations in 1942 as a bombardment squadron before being reorganized in 1964. Its mission shifted to maintain nuclear deterrence through the operation of ballistic missile systems.

The squadron's name and number trace to the 321st Bombardment Squadron of 1942, whose B-24 crews flew from Queensland against Japanese shipping and airfields; the unit earned Distinguished Unit Citations for Papua and for the Wewak strikes of September 1943. Its Minuteman III alert mission at F.E. Warren continues that lineage.

Personnel maintain constant operational readiness throughout each day and night with rotating shifts. Training and system checks occur regularly to ensure all equipment functions properly.

The 321st won the Samuel C. Phillips Award as the best missile squadron in Air Force Space Command in 2005, 2010 and 2019. It activated on 9 April 1964 with fifty LGM-30B Minuteman I missiles, the third of the 90th Wing's four Minuteman squadrons to come online.