The S-25 Berkut (Russian: С-25 «Беркут»; "Berkut" means golden eagle in English) is a surface-to-air guided missile, the first operational SAM system in the Soviet Union. It was deployed in several rings around Moscow starting in 1955 and became combat ready in June 1956. It was used only to defend Moscow, the more mobile S-75 (SA-2 Guideline) would be used in almost all other roles. Several improvements were introduced over its long service lifetime, and the system was finally replaced by the S-300P in 1982.
Its NATO reporting name is SA-1 Guild. S-25 is short for Systema 25, referring to the entire system of missiles, radars, and launchers. Portions of the system include the V-300 missile, R-113 and B-200 radars, and A-11/A-12 antennas for the B-200.