Kelly

The O'Kellys (Irish Ó Ceallaigh) were the chiefly dynasty of Uí Maine, one of the oldest and largest kingdoms of Connacht, stretching across eastern Galway and southern Roscommon. Native genealogies traced them to Maine Mór, founder of the Uí Maine line. They supplied its kings through the medieval centuries, and in 1337 the O'Kelly chief still ruled the subject kingdom.

The Book of Uí Maine, an Irish genealogical codex, was compiled around 1392 to 1394 at the request of Muircertach Ó Ceallaigh, bishop of Clonfert and later archbishop of Tuam, and kept by the clan until 1757.

In 1503 the Clanricarde Burkes sacked O'Kelly castles, and the feud drew Maelsechlainn Ó Cellaigh, king of Uí Maine, into the battle of Knockdoe in 1504.