Harold Anthony Caccia, Baron Caccia (21 December 1905 Pachmarhi, India; 31 October 1990 Builth Wells, Wales) was a British diplomat.
He was educated at Eton College and Trinity College, Oxford and won a Blue at rugby union, playing at centre for Oxford in The Varsity Match in 1926. He played cricket for Oxfordshire in the Minor Counties Championship between 1928 and 1938. He married Anne Catherine Barstow, daughter of George Lewis Barstow and Enid Lillian Lawrence, in 1932. He entered the diplomatic service in 1929 and was posted to Peking (Beijing) and then to Athens and London where, in 1936, he became assistant private secretary to Anthony Eden.
He was back in Athens early in World War II, but was then attached to the staff of Harold Macmillan, Britain's representative at Allied headquarters in North Africa. The Greek civil war once again saw him in that country, and by 1945 his services earned him recognition on the Birthday Honours List. He was knighted in 1950.
He was created a life peer with the title Baron Caccia, of Abernant in the County of Breconshire, on 11 May 1965. Caccia was appointed a Bailiff Grand Cross of the Order of the Hospital of St John of Jerusalem, a Knight Grand Cross of the Royal Victorian Order and a Knight Grand Cross of the Order of St Michael and St George.
Caccia was Ambassador to Austria from 1951 to 1954, and from 1956 to 1961 Ambassador to the USA. He was sent to Washington to repair relations badly damaged by the Suez crisis of 1956. The breakdown in mutual confidence arose when Britain and France joined an Israeli invasion of Egypt and sent military forces to capture the Suez Canal, which had been nationalized by President Gamal Abdel Nasser of Egypt. In the years that followed, he was instrumental in restoring and nurturing the "special relationship" between London and Washington.
In 1961, he became Permanent Under-Secretary of State, an office he held until 1965. He was Provost of Eton 1965-78.