Cellach mac Fíonachta

Cellach mac Fíonachta, fl. 9th century, ancestor of Ó Ceallaigh of County Galway.
Cellagh was a grandson of king Ailell mac Inreachtach of Uí Maine. He never became king himself, but his grandchildren and their descendants, the Uí Ceallaigh, monopolised the kingship. The first Ó Ceallaigh ruler was Aodh Ua Cellaigh, who was killed at the battle of Clontarf, fighting on the side of Brian Boru. His last descendant to rule the kingdom was Feardorcha Ó Cellaigh. Ó Ceallaigh, O'Kelly and Kelly is one of the most populous surnames in County Galway.