Cernach is a given name which may refer to:
Saint Cernach, 6th-century Welsh saint, abbot and confessor Cernach mac Congalaig (died 818), an Irish king of Brega Cernach mac Fergusa (died 805), a king in southern Brega Cernach mac Fogartaig (died 738), a king in southern Brega
See also Conall Cernach, a hero in Irish mythology