Ragnall Mac Gilla Muire was a twelfth-century leading figure of Waterford. He was one of several men taken prisoner by the English in 1170, when Waterford was captured by Richard de Clare. Ragnall is noted by a fourteenth-century legal enquiry which sought to determine whether a slain man was an Ostman—and thus entitled to English law—or an Irishman. Ragnall may the eponym of Reginald's Tower.