Maelgwn was a generous contributor to the cause of Christianity throughout Wales. He made donations to support Saint Brynach in Dyfed, Saint Cadoc in Gwynllwg, Saint Cybi in Anglesey, Saint Padarn in Ceredigion, and Saint Tydecho in Powys. He is also associated with the foundation of Bangor, but hard evidence of this is lacking. In his 1723 "Mona Antiqua Restaurata", Henry Rowlands asserts that Bangor was raised to an episcopal see by Maelgwn in 550, but he provides no source for the assertion.