Saint Gwynllyw Milwr or Gwynllyw Farfog, known in English in a corrupted form as Woolos the Warrior or Woolos the Bearded (Latin: Gundleus, Gundleius or Gwenleue) (c. 450 – c. 500) was a Welsh king and religious figure.

He was King of Gwynllwg in South Wales and is the legendary founder and patron saint of the City of Newport living around the 5th century. According to medieval tradition he was a feared warlord and raider who knew King Arthur, but later found religion and became a hermit founding St Woolos Cathedral in Newport. He was the father of one of the most revered Welsh saints, Saint Cadoc the Wise.

The medieval lives of Saint Cadoc (c. 1100) by Lifris and of Saint Gwynllyw (c. 1120) preserve legendary details of Gwynllyw, though details frequently differ. He is also noted in Welsh king lists. The saint’s lives note that his deeds were celebrated by Welsh bards, indicating he had a widespread popular following. Although saints' lives frequently exaggerate it does seem likely that a monarch of this name existed and a core element in the lives may contain some true details.