Glywys Cernyw

Saint Glywys Cernyw was a Welsh saint of the sixth century. He was the son of Gwynllyw, a ruler of Gwynllŵg, and his wife Gwladys, and a brother of Saint Cadoc. He died a martyr, at the place called Merthyr Glywys.

His name appears in an addition to Plant Brychan, where he is called the brother of Saint Cadoc. Iolo Morganwg makes him the saint of the church of Coedcernyw, in Gwynllŵg, but in truth that church is dedicated to All Saints.

He is also remembered in the Book of Llandaff. There his son gave land to God and to Saints Dubricius and Teilo, into the hands of Bishop Gwytlon, suffragan of Teilo, and gave to the Church of Llandaff a man with his descendants, as servants forever. No further details of the saint are known.