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a Catholic monastic order founded in southern Italy as a branch of the Benedictine Order in the mid-13th century by the monk Pietro di Morrone (later Pope Celestine V; hence the name of the congregation). In 1263 the Celestines adopted the Benedictine Rule. They founded a large number of monasteries in Italy, France, Germany, the Netherlands, and Bohemia. The order ceased to exist at the turn of the 19th century.