Sir (Frederick) Elwyn Elwyn-Jones, Baron Elwyn-Jones, PC (24 October 1909, Llanelli-4 December 1989) was a British barrister and politician.

Jones read law at the University of Wales, Aberystwyth, and Gonville and Caius College, Cambridge. He became a barrister and Recorder (judge) of Merthyr Tydfil. He was also a broadcaster and journalist. He served as junior British Counsel during the Nuremberg Trials and the Hamburg trial of Marshal Erich von Manstein in 1945-6. He had spent time in Germany in the 1930s as a young man.

At the 1945 general election, Jones was elected as Labour Member of Parliament for Plaistow, East London. In 1950, he became MP for West Ham, South, serving until 1974.

Jones was appointed by Harold Wilson as Attorney General, serving from 1964 to 1970. He led the prosecution of Myra Hindley and Ian Brady during this time. In February 1974, he was once again elected, for Newham, South, but left the House of Commons soon afterwards when he was made a life peer, as Baron Elwyn-Jones, of Llanelli in the County of Carmarthen and of Newham in Greater London. He became Lord Chancellor from 1974 to 1979, under Harold Wilson and James Callaghan. He became a Privy Counsellor in 1964.