The 851st Strategic Missile Squadron is an inactive United States Air Force unit. It was last assigned to the 456th Strategic Aerospace Wing, stationed at Beale Air Force Base, California. It was equipped with the HGM-25A Titan I intercontinental ballistic missile, with a mission of nuclear deterrence. It was the last Titan I squadron to achieve alert status on 1 February 1961. The squadron was inactivated as part of the phaseout of the Titan I on 25 March 1965.