The brother of Diarmait mac Cerbaill, future High King of Ireland.
Prof. Byrnes writes "In 538 Diarmait mac Cerbaill's brother Maine (the coincidence of his name is quite fortuitous) was defeated and slain at the battle of Claenloch near Gort in south Galway.
In the minds of compilers this meant that he was over-king of the Southern Ui Neill, but this is probably an anachronism, especially since Tuathal Maelgarb is supposed to have been high-king of Tara at this date."
The Annals of the Four Masters (who list his death sub anno 531), state: Cath Claonlocha h-i c-Cenel Aodha ria n-Goibhneann, taoisioch Ua Fiachrach Aidhne, airm in ro marbhadh Maine, mac Cerbhaill, ag cosnamh geillsine Ua Maine Connacht.
The battle of Claenloch, in Cinel Aedh, by Goibhneann, chief of Ui Fiachrach Aidhne, where Maine, son of Cearbhall, was killed, in defending the hostages of Ui Maine of Connaught.