Maelsechlainn mac Tadhg Ó Cellaigh, King of Uí Maine, Chief of the Name, was a leading participant in the Battle of Knockdoe, fl.
Maelsechlainn is believed to have been the son of a previous king, Tadhg Caech Ó Cellaigh, who died in 1476.
In 1503, the then lord, Ulick Fionn Burke "gave a very great overthrow to O'Kelly at a party of the people of Conmaicne-Cuile, where a great part of the gallowglasses of both the Clann-Donnell and Clann-Sweeny were slain around their constables, and where Walter, the son of John Burke, a distinguished captain, was also slain in this conflict.
In the resulting Battle of Knockdoe, Ó Cellaigh fought on the side of Gerald FitzGerald, 8th Earl of Kildare, Lord Deputy of Ireland.
Ó Cellaigh accompanied FitzGerald and lifted Burke's occupation of Galway and Athenry.