Clan Barrett (Irish: Clann Bairéad) is an Irish clan from County Cork that originally descended from Norman invaders who travelled through England and Wales with William the Conqueror in the 12th century, and then into Ireland with Strongbow in the 13th century. They are often thought to be related to the ancestors of the similarly-named Clan Barrett of the mountainous Mayo-Galway areas, who are otherwise considered Gaelic in origin. Of the two, the Cork branch was considered numerically stronger, while the Mayo-Galway branch held more prominence in the Middle Ages.