Dyfnwal Hen or Dumnagual Hen ("Dyfnwal the Old") was a ruler of the Brittonic kingdom of Alt Clut, later known as Strathclyde, probably sometime in the early 6th century. His biography is vague, but he was regarded as an important ancestor figure for several kingly lines in the Hen Ogledd or "Old North" of Britain. As an ancestor figure, he compares to Coel Hen, another obscure figure credited with founding a number of northern dynasties.