Ceretic ap Gwallog was the last king of Elmet, a Brythonioc kingdom that existed in the north of Britain during sub-Roman times. It is believed he was driven into exile in either 616 or 626 following the final defeat of his people in war with the northern Angles of Northumbria. It is written that he died a couple of years later at the court of the king of Kingdom of Gwynedd. His realm was annexed by Northumbria.