Mark of Cornwall was a sixth-century King of Kernow (Cornwall), possibly identical with King Conomor. He is best known for his appearance in Arthurian legend as the uncle of Tristan and the husband of Iseult who engages with Tristan in a secret liaison, giving Mark the epithet "Cuckold King".

Conomor, 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.