Coel (Old Welsh: Coil) or Coel Hen ("Coel the Old") is a figure prominent in Welsh literature and legend since the Middle Ages. Early Welsh tradition knew of a Coel Hen (Coel the Old), a leader in Roman or Sub-Roman Britain and the progenitor of several kingly lines in the Hen Ogledd ("the Old North"), the Brittonic-speaking part of northern England and southern Scotland. Later medieval legend told of a Coel, apparently derived from Coel Hen, who was the father of Saint Helena and the grandfather of Roman Emperor Constantine the Great. Other similarly named characters may be confused or conflated with the Welsh Coel. The legendary "King Coel" is sometimes supposed to be the historical basis for the popular nursery rhyme "Old King Cole", but this is unlikely.

Coel (Old Welsh: Coil) or Coel Hen ("Coel the Old") is a figure prominent in Welsh literature and legend since the Middle Ages. Early Welsh tradition knew of a Coel Hen (Coel the Old), a leader in Roman or Sub-Roman Britain and the progenitor of several kingly lines in the Hen Ogledd ("the Old North"), the Brittonic-speaking part of northern England and southern Scotland. Later medieval legend told of a Coel, apparently derived from Coel Hen, who was the father of Saint Helena and the grandfather of Roman Emperor Constantine the Great. Other similarly named characters may be confused or conflated with the Welsh Coel. The legendary "King Coel" is sometimes supposed to be the historical basis for the popular nursery rhyme "Old King Cole", but this is unlikely.