Order of Cistercians of the Strict Observance

The Order of Cistercians of the Strict Observance (O.C.S.O.: Ordo Cisterciensis Strictioris Observantiae) is a Roman Catholic religious order of cloistered contemplative monastics who follow the Rule of St. Benedict. A branch of the Order of Cistercians, they have communities of both monks and nuns, commonly referred to as Trappists and Trappistines, respectively.