Rollo (rŏl´ō) or Hrolf (rŏlf), c.860–c.932, first duke of Normandy. As leader of the Norman pirates settled at the mouth of the Seine, he attacked (910) Paris and Chartres. By the Treaty of Saint-Clair-sur-Epte (911) with King Charles III of France, he received in fief the territory his men had occupied (part of the future duchy of Normandy) on condition that he defend it against attack and that he receive baptism. Rollo was baptized (912) as Robert. He supported Charles against Raoul, from whom he obtained additional territory. He was succeeded by his son William Longsword. Rollo's direct descendants included William the Conqueror.