BASILEUS, (βασιλεύς, king or lord), a title assumed by the emperors of Constantinople, exclusive of all other princes, to whom they gave the title of rex. The title basileus was subsequently assumed by other kings, particularly the kings of England; as Ego Edgar totius Anglie basileus confirmavi. Hence also the queen of England was anciently styled Basilea or Basilissa. See ARCHON, and KING.