Cunedagius (Latinized form; Welsh: Cunedda[1]) was a legendary king of the Britons, as recounted by Geoffrey of Monmouth.
[2] He was the son of Henwin, Duke of Cornwall, and Regan, the daughter of King Leir.
Following Cordelia's Suicide, Cunedagius came to rule the region of Britain southwest of the Humber.
[3] Geoffrey synchronizes Cunedagius' reign with the ministry of the Jewish prophet Isaiah and the founding of Rome by Romulus and Remus.
Cunedagius and Marganus' conflict is mentioned twice in Thomas Norton and Thomas Sackville's play Gorboduc (1561), as a warning against the possibility of civil strife: "Morgan slaine did yeld his conquered parte unto his cosins sworde in Camberland" (Act I, Scene II); "the cruell sworde bereft Morgan his life with cosyns hand" (Act III, Scene I).