Hugh Swynnerton Thomas, Baron Thomas of Swynnerton (born 21 October 1931) is an English historian and writer. He sits in the House of Lords as a crossbencher.
Thomas was born 21 October 1931 in Windsor, England, to Hugh Whitelegge Thomas, a colonial commissioner, and his wife Margery Angela Augusta née Swynnerton. Sir Shenton Thomas was his uncle. He was educated at Sherborne School in Dorset, before taking a BA in 1951 at Queens' College, Cambridge, where he was a major scholar and is now an Honorary Fellow. Thomas gained a first class in Part I of the History Tripos in 1952 and was president of the Cambridge Union Society in 1953. He also studied at the Sorbonne in Paris.
From 1954 to 1957, Thomas worked in the Foreign Office partly as secretary of the British Delegation to the sub-committee of the UN Disarmament Commission. From 1966 to 1975, he was professor of History at the University of Reading, and chairman of the European committee. Thomas was then chairman of the Centre for Policy Studies in London from 1979 to 1991, which worked for Prime Minister Margaret Thatcher.