Gruffydd Young (or Griffin Yonge) (c. 1370 – c. 1435) was a cleric and a close supporter of Owain Glyndŵr during his Welsh rebellion against the EnglishKing Henry IV between 1400 and 1412.
He was closely involved in Owain's strategy and formulated the Pennal Policy in which Owain stated that he would transfer the allegiance of the Welsh church away from Rome to the Antipope Benedict XIII in Avignon.
In 1407 he managed to gain the role of Bishop of Bangor after intrigues against the incumbent BishopLlywelyn Byford and within a few months ensured his own transfer to St. Davids where if the Pennal Policy had come into effect he would have become the primate of the Church in Wales.
Setbacks
By 1408 as the rebellion was experiencing setbacks he made his own future plans. Outside events were leading towards the Council of Constance which soon brought the schism of two competing Popes to an end with the election of Pope Martin V. The Pennal Policy was to become redundant. Young instead was appointed as Bishop of Ross in the Kingdom of Scotland, by Pope Martin V, but he was never really in firm control of his diocese and was transferred to become titular Bishop of Hippo in North Africa along with two livings in Rheims and Tours in France.