Bladud or Blaiddyd was a legendary king of the Britons, for whose existence there is no historical evidence. He is first mentioned in Geoffrey of Monmouth's Historia Regum Britanniae, which describes him as the son of King Rud Hud Hudibras, and the tenth ruler in line from the first King, Brutus. A Bleydiud son of Caratauc is mentioned in the Welsh Harleian MS 3859 genealogies, suggesting to some that Geoffrey misinterpreted a scrap of Welsh genealogy (such as the Harleian genealogies or a related text). The Welsh form of the name is given as Blaiddyd in manuscripts of the Brut Tysilio (Welsh translations of Geoffrey's Historia). The meaning of the name is "Wolf-lord" (Welsh blaidd "wolf" + iudd "lord"). In the text he is said to have founded the city of Bath. He was succeeded by his son Leir (King Lear).
The tale of Bladud was later embellished by other authors, such as John Hardyng and John Higgins, writing in the sixteenth century.
According to the final form of the legend, Bladud was sent by his father to be educated in the liberal arts in Athens. After his father's death he returned, with four philosophers, and founded a university at Stamford in Lincolnshire, which flourished until it was suppressed by Saint Augustine of Canterbury on account of heresies which were taught there. Supposedly he ruled for twenty years from 863 BC or perhaps 500 BC, in which time he built Kaerbadum or Caervaddon (Bath), creating the hot springs there by the use of magic. He dedicated the city to the goddess Athena or Minerva, and in honour of her lit undying fires, whose flames turned to balls of stone as they grew low, with new ones springing up in their stead: an embellishment of an account from the fourth-century writer Solinus of the use of local coal on the altars of her temple.