De Sanctimoniali de Wattun or On the Nun of Watton is a 12th-century miracle story, describing events which took place in Yorkshire in the mid-12th century at the nunnery of Watton, East Riding of Yorkshire. It is also called A Certain Wonderful Miracle. De Sanctimoniali de Wattun survives in one manuscript, MS Corpus Christi College 139. It is thought to have been written around 1160. The author is usually thought of as the Cistercian abbot Ailred of Rievaulx, an identification that is probable if not certain. The author's source for the events described were the older nuns of the monastery.