Flann Óge Ó Domhnalláin (died 1342) was Chief Poet of Connacht.
Ó Domhnalláin was a member of an Irish family of Bards, originally located in Ballydonnellan, County Galway.
A sept of the Uí Maine called Clann Breasail, they held the position of "Cathmhaol" or Battle Champion.
Descendants of the Uí Domhnalláin are still found in Galway and Roscommon under the surname Donnellan.
He was a descendant of King Dluthach mac Fithcheallach of Ui Maine.