Reginald's Tower was built by the Normans when they came to Waterford. The tower's name is derived from a form of the Irish name "Raghnall". The tower's name seems to refer to one of the many Viking rulers of the town that bore the name. It might be Ragnall mac Gillemaire, the last Norse ruler of the town. The tower was probably built in the 13th or 14th century; it may have been constructed between 1253 and 1280. In 1185 Prince John of England landed in Waterford and organised the rebuilding of the city walls, including the tower.