Gwenddoleu ap Ceidio (died c. 573) or Gwenddolau was a Brythonic king who ruled in Arfderydd (now Arthuret). This is in what is now south-west Scotland and north-west England in the area around Hadrian's Wall and Carlisle during the sub-Roman period in Britain. Carwinley near Longtown north of Carlisle is thought to represent Caer Wenddolau or Gwenddolau's Fort. Genealogies make him a descendant of Coel Hen, who is believed to have ruled much of what is now southern Scotland and the Borders following the Roman withdrawal from the island of Britain, in the area known as the Hen Ogledd. Gwenddoleu was therefore likely to have been either the heir to one of the many successor states of Coel Hen's realm or an usurper who claimed descent from Coel Hen to legitimize his family's claim to the region.