Galwyddel was a Brythonic kingdom within the Hen Ogledd ("Old North") in Sub-Roman Britain. Its area corresponds to modern-day Galloway, Scotland. Galwyddel is believed to have split from the Kingdom of Alt Clut following the death of King Cinuit and his land's division between his sons: Dyfnwal Hen (who became King of Alt Clut); and Tudwal (who became the first King of Galwyddel). Galwyddel is believed to have maintained authority over the Isle of Man. Around 550, Galwyddel was invaded and annexed by the Kingdom of Rheged, under King Urien. The Galwyddel King, Senyllt, was forced to flee to Ynys Manau (Isle of Man).