Dindaethwy was in medieval times one of two commotes of the cantref of Rhosyr, in the south-east of the Isle of Anglesey.
Later in the Middle Ages, Llywelyn the Great founded a monastery at Llanfaes; his wife Siwan was buried there.
Later, Dindaethwy was the home of Penmynydd, the family estate of the Tudors of Anglesey.
The Daethwy were the local Celtic tribe, who also gave their name to the village of Porthaethwy (Menai Bridge).
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