William Glyn (1504 – 21 May 1558), also known as William Glynn or William Glynne, was the Bishop of Bangor from 1555 until his death. He was born in Heneglwys, Anglesey and educated at Queens' College, Cambridge, later becoming a fellow of that college and of Trinity. He was elected President of Queens' College in 1553, Vice-Chancellor of Cambridge University in the following year, and Bishop of Bangor in 1555. He had been pragmatic towards the religious changes of the Reformation but probably remained most sympathetic to Catholicism.