John Keiran Barry Moylan Nicholas (1919–2002) was a British legal scholar. He was Professor of Comparative Law at the University of Oxford from 1971 to 1978, and Principal of Brasenose College, Oxford from 1978 to 1989.
Nicholas was born on 6 July 1919 to Archibald John Nicholas and Rose (née Moylan). He was educated at Downside School, a Catholic independent school in Somerset, England. He then matriculated into Brasenose College, Oxford where he was a scholar and studied classics: he achieved first class honours in Mods in 1939. Having taken a break from university to serve in the war, he returned to his college to study Jurisprudence: he graduated with a first class Bachelor of Arts (BA) degree in 1946.
He began teaching at Brasenose College, Oxford in 1946, and served as Principal of the college from 1978 to 1989. He gave up the position at the appointed age of 70, but he did not retire. He additionally served as All Souls Reader in Roman Law from 1949 to 1971, and Professor of Comparative Law at the University of Oxford from 1971 to 1978.
There is an obituary notice  by Peter Birks for the British Academy.
- 'NICHOLAS, (John Keiran) Barry (Moylan)', Who Was Who, A & C Black, an imprint of Bloomsbury Publishing plc, 1920–2016; online edn, Oxford University Press, 2014; online edn, April 2014 accessed 19 June 2017
- Judge, Harry (9 March 2002). "Obituary: Barry Nicholas". The Guardian. Retrieved 19 October 2018.
H. L. A. Hart
| Principal of Brasenose College, Oxford