John Dyson Heydon (born 1 March 1943) is a former Justice of the High Court of Australia, the highest court in the Australian court hierarchy, who served from 2003 to 2013.
A graduate of the University of Sydney and the University of Oxford (attending the latter as a Rhodes Scholar), Heydon had previously served as Dean of the Sydney Law School and as a Justice of the New South Wales Court of Appeal.
He retired from the court at the constitutionally mandated age of 70, and has gone on to chair the Royal Commission into trade union governance and corruption.