Tadhg Caech Ó Cellaigh, King of Ui Maine, retired 1476.
Upon the death of Aedh na gCailleach Ó Cellaigh in 1469, the Ui Maine elected two kings, ruling Iar Ui Maine (west) and Airthir Ui Maine (east) respectively. They were Tadhg Caech Ó Cellaigh of Airthir, and William in the west. Upon the retirement of Tadhg in 1476, Uilliam became king of all Ui Maine, installing his brother, Donnchadh, as tainiste in Airthir.
References
Tadhg Caech Ó Cellaigh Wikipedia(Text) CC BY-SA