Cyngar ap Geraint was a Welsh monk and hermit who lived during the late 5th and early 6th centuries. Born in Gwynedd as the son of King Gerren Llyngesog, he became a follower of his nephew, Saint Cybi Felyn. His religious life involved significant missionary work, including the construction of several churches in South Wales and a four-year period spent building churches on the island of Aran Mor in Ireland. He is primarily remembered for his monastic foundations in Wales.