Conomor (fl. c. 540), also known as Conomerus or Conomor the Cursed, was an early medieval ruler of Brittany. His name, which has the Welsh cognate Cynfawr, means "Great Dog", but could also indicate "Sea Dog" in early Brythonic. Conomor was notorious for his cruelty, becoming a legendary villain in Breton culture. He is widely regarded as one of the probable sources for the myth of Bluebeard and possibly also of Tristan's uncle King Mark of Cornwall. The wife-beating giant Cormoran may also retain a garbled folk memory of the same character.
Conomor was king of Dumnonia and Prince of Poher. Dumnonia was, at this time, expanding to claim control over all Brythonic territory in Armorica (Brittany). It is difficult to disentangle the Conomor of legend from the historical ruler. As with other early Breton rulers most written information about him comes from the lives of Breton saints.