mutual security organization dating from 1955 to 1979 and composed of Turkey, Iran, Pakistan, and the United Kingdom. Until March 1959 the organization was known as the Middle East Treaty Organization, included Iraq, and had its headquarters in Baghdad.

Formed at the urging of Britain and the United States, the Central Treaty Organization was intended to counter the threat of Soviet expansion into vital Middle East oil-producing regions. It was never very effective. Iraq withdrew from the alliance in 1959 after its anti-Soviet monarchy was overthrown. That same year the United States became an associate member, the name of the organization was changed to CENTO, and its headquarters was moved to Ankara. Following the fall of the shah in 1979, Iran withdrew, and CENTO was dissolved.