Cynddylan, or Cynddylan ap Cyndrwyn (Cynddylan son of Cyndrwyn) was a seventh-century ruler associated with Pengwern. He is described in the poem Marwnad Cynddylan (Elegy of Cynddylan) as a king of Dogfeiling, a sub-kingdom of Gwynedd near to Rhuthun in the middle of Denbighshire, in modern-day Wales.