Saint Cadoc or Cadog was a 5th–6th-century Abbot of Llancarfan, near Cowbridge in Glamorgan, Wales, a monastery famous from the era of the British church as a centre of learning, where Illtud spent the first period of his religious life under Cadoc's tutelage. Cadoc is credited with the establishment of many churches in Cornwall, Brittany, Dyfed and Scotland. He is known as Cattwg Ddoeth, "the Wise", and a large collection of his maxims and moral sayings were included in Volume III of the Myvyrian Archaiology. He is listed in the 2004 edition of the Roman Martyrology under 21 September. His Norman-era "Life" is a hagiography of importance to the case for the historicity of Arthur as one of seven saints' lives that mention Arthur independently of Geoffrey of Monmouth's Historia Regum Britanniae.

Illtud, also known as Illtud Farchog or Illtud the Knight, is venerated as the abbot teacher of the divinity school, Bangor Illtyd, located in Llanilltud Fawr in Glamorgan, Wales. He founded the monastery and college in the 6th century, and the school is believed to be Britain's earliest centre of learning. At its height, it had over a thousand pupils and schooled many of the great saints of the age, such as David, Samson of Dol, and the historian Gildas.