Celestines were a Roman Catholic monastic order, a branch of the Benedictines, founded in 1244. At the foundation of the new rule, they were called Hermits of St Damiano, or Moronites (or Murronites), and did not assume the appellation of Celestines until after the election of their founder, Peter of Morone (Pietro Murrone), to the Papacy as Celestine V. They use the post-nominal initials O.S.B. Cel.
The fame of the holy life and the austerities practised by Pietro Morone in his solitude on the Mountain of Majella, near Sulmona, attracted many visitors, several of whom were moved to remain and share his mode of life. They built a small convent on the spot inhabited by the holy hermit, which became too small for the accommodation of those who came to share their life of privations. Peter of Morone (later Pope Celestine V), their founder, built a number of other small oratories in that neighborhood.
About the year 1254, Peter of Morone gave the order a rule formulated in accordance with his own practices. In 1264 the new institution was approved as a branch of the Benedictines by Urban IV; however, the next pope Pope Gregory X had commanded that all orders founded since the prior Lateran Council should not be further multiplied. Hearing a rumor that the order was to be suppressed, the reclusive Peter traveled to Lyon, where the Pope was holding a council. There he persuaded Gregory to approve his new order, making it a branch of the Benedictines and following the rule of Saint Benedict, but adding to it additional severities and privations. Gregory took it under the Papal protection, assured to it the possession of all property it might acquire, and endowed it with exemption from the authority of the ordinary. Nothing more was needed to ensure the rapid spread of the new association and Peter the hermit of Morone lived to see himself "Superior-General" to thirty-six monasteries and more than six hundred monks.