Robert Anthony Eden, 1st Earl of Avon (12 June 1897 – 14 January 1977) was a British Conservative politician, who was Prime Minister from 1955 to 1957. He was also Foreign Secretary for three periods between 1935 and 1955, including during World War II. He is best known for his outspoken opposition to appeasement in the 1930s, his diplomatic leadership in the 1940s and 1950s, and the failure of his Middle East policy in 1956 that ended his premiership.
Eden's worldwide reputation as an opponent of appeasement, a "Man of Peace", and a skilled diplomat was overshadowed in the second year of his premiership when the United States refused to support the Anglo-French military response to the Suez Crisis, which critics across party lines regarded as an historic setback for British foreign policy, signalling the end of British predominance in the Middle East. Most historians argue that he made a series of blunders, especially not realising the depth of opposition to military action by the United States. Most historians say that Eden completely dominated the British decision-making process in the Suez crisis. However, Jonathan Pearson argues in Sir Anthony Eden and the Suez Crisis: Reluctant Gamble (2002) that Eden was more reluctant and less bellicose than most historians say.
He is generally ranked among the least successful British Prime Ministers of the 20th century, although two broadly sympathetic biographies (in 1986 and 2003) have gone some way to redressing the balance of opinion. D.R. Thorpe says the Suez Crisis "was a truly tragic end to his premiership, and one that came to assume a disproportionate importance in any assessment of his career."