William Averell Harriman (1891—1986) was a US politician and diplomat. An alumnus of Yale, he was appointed ambassador to the USSR in 1943 and to Great Britain in 1946. Domestically he was Secretary of Commerce (1946–48) and as special assistant to President Harry S Truman from 1950 to 1951 helped to organize NATO.
From 1951 to 1953 he was the Director of the Mutual Security Agency. After this he served as Governor of New York from 1955 to 1959. Further diplomatic assignments saw him as ambassador-at-large (1961 & 1965-68) and then as the US representative at the Vietnam peace talks in Paris (1968).
In 1963 Harriman negotiated the partial Nuclear Test-Ban Treaty between the USA and the Soviet Union. He remained a valuable servant of the US government, making frequent visits to Moscow, the last of which was made in 1982 when he was 91.