Maelsuthan Ua Cerbhail, Maelsuthain O'Carroll, or Maelsuthain O'Cearbhail (died 1010)[1] was a political and academic figure in medieval Ireland. He was lord of the Eóganacht Locha Léin,[2] advisor to High King Brian Boru, and an important scholar often credited for beginning the Annals of Innisfallen.[3] Maelsuthan's academic reputation was considerable, earning him accolades like "chief doctor of the Western world in his time" and "sage of Ireland."[4]