Saint Gwladys ferch Brychan (Welsh: [ˈɡwlaːdɪs]) or St Gladys (Latin: Gladusa), daughter of King Brychan of Brycheiniog, [1] was the queen of the saint-king Gwynllyw Milwr and the mother of Cadoc "the Wise", whose Vita may be the earliest saint's life to mention Arthur.

[4][5] Both saint's lives agree that Gwladys, daughter of Brychan married Gwynllyw and gave birth to Cadoc.

[6][7] In the Life of Saint Gwynllyw, the king is just and fair and the marriage is accomplished peacefully,[8] while the tale of Glwadys' marriage in Lifris' work seems similar to abduction stories in other saints' lives as well as in other Arthurian stories, which may suggest that it is myth rather than history.

It was the prompting of Cadoc and Gwladys that led Gwynllyw to abandon his life of violence and seek forgiveness for his sins.

Gwladys accompanied Gwynllyw into a hermits life and for a while they lived together there fasting or on a vegetarian diet and bathing in the cold waters of the Usk but moved apart to avoid temptation: Gwladys founded a hermitage at Pencarn in Bassaleg, supposedly at Pont Ebbw,[11] where there is a supposed grave and where she is said to have bathed in the Ebbw River, though Cadoc's life says that she later moved to Capel Wladus in Gelligaer.