Bryn Euryn is a hillfort and associated manor house near Conwy, north Wales. The hillfort itself does not necessarily date to the Iron Age period, but is associated with Cynlas the Red, the King of Rhos in the early 6th century. The local name for the site is Dinerth, Fort of the Bear. Cynlas is notable for having been one of the five “tyrants of Britain” denounced for his sins by the chronicler, Gildas.

Excavations revealed a “massive well-built” limestone wall, up to three meters high and the site commands extensive views of the Conwy Valley. Eventually, the Kingdom of Rhos became a cantref, or administrative unit, of the Kingdom of Gwynedd and the hillfort was abandoned in favor of the manor house known now as Llys Euryn. This house is thought to have been built at least by 1240 AD by Ednyfed Fychan, ancestor of the Tudor dynasty and steward to Llywelyn Fawr, the ruler of Wales.

Today, the ruined house is open on one side, but has standing walls on the three remaining, with an intact fireplace and chimney. It is thought that this version of the house was constructed in the 15th century, after an earlier house was destroyed during the time of Owain Glyndwr.

After 1283 and the Norman conquest of Wales, the house was given over to the Earl of Lincoln, who ruled his portion of Wales from Denbigh. By the 17th century, it was abandoned and used to store blasting materials for the nearby quarry.