Cunedagius (Welsh: Kynedda) was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of Henwinus , Duke of Cornwall, and Regan, the daughter of King Leir.
Cunedagius was a legitimate male heir of Leir and despised the rule of the queen, Cordelia, in Britain. With the help of his cousin Marganus, Cunedagius took over the kingdom from Cordelia and ruled half of it. Following Cordelia's suicide, Cunedagius came to rule the region of Britain southwest of the Humber.
Two years after they split the island, Marganus invaded Cornwall and destroyed much of the land. Cunedagius met him in battle and defeated him. Marganus fled throughout Britain until he was cornered in Wales. Cunedagius killed him and became king of all of Britain. He ruled all of Britain for 33 years and was succeeded by his son, Rivallo.
It is written that in during his reign, Isaiah was making his prophesies in Israel, and Romulus and Remus found Rome.
