Cwyllog

Saint Cwyllog (Cywyllog) was a holy woman of Wales who lived in the early 6th century on the island of Anglesey. Little is known for certain about her; her dates of birth and death are not preserved, and her unusual name points to a Celtic origin.

She was, according to tradition, a daughter of Caw (or Coel) of Rheged, one of the chieftains of the Old North, who lost his lands and fled with his family to the north-⁠east of Anglesey. Maelgwn of Gwynedd gave him land there in the district of Twrcelyn, on condition that the family devote themselves to the religious life and not seek a country of their own. Cwyllog had three sisters, Cain, Peithien and Gwenafwy, and several brothers, among them Saints Gildas, Allgo and Eugrad; the number of Caw's children varies from ten to twenty-⁠one, depending on the manuscript.

She is said to have been the wife of Medrod (Mordred), the nephew of King Arthur, and, after his death in the battle of Camlann, around 537, to have turned to the religious life. She is credited with founding the church of Llangwyllog, in the middle of Anglesey, where a church still bears her name. Her day is 7 January, by the Western calendar (new style).