Robert Anthony Eden, 1st Earl of Avon, KG, MC, PC (12 June 1897 – 14 January 1977) was a British Conservative politician who served as Prime Minister of the United Kingdom from 1955 until his resignation in 1957. Eden is generally considered to be among the least successful of British prime ministers in the 20th century, although two broadly sympathetic biographies have gone some way to shifting the balance of opinion. He was the first out of fifteen British prime ministers to be appointed by Queen Elizabeth II in her seventy-year reign.