Sir John Rhys was a Welsh scholar, fellow of the British Academy, Celticist and the first Professor of Celtic at Oxford University.
In 1874 Rhys delivered a series of lectures in Aberystwyth, later published as Lectures on Welsh Philology, which served to establish his reputation as a leading scholar of the Celtic language. This reputation saw him appointed as the first Professor of Celtic at Oxford University in 1877. He was also made a Fellow of Jesus College, Oxford. Rhys was elected bursar of the college in 1885, a position he held until 1895, when he succeeded Daniel Harper as principal.