The Benedictine Confederation is a union of monastic congregations that nevertheless retain their own autonomy, established by Pope Leo XIII in his brief "Summum semper" (12 July 1893), subsequently approved by his successors. Pope Pius XII explicitly ordered this union to be regulated by a "Lex Propria", which was later revised after the Second Vatican Council.
Most Benedictine houses are loosely affiliated in 20 national or supra-national congregations. Each of these congregations elects its own Abbot President. These presidents meet annually in the Synod of Presidents. Additionally, there is a meeting every four years of the Congress of Abbots, which is made up of all abbots and conventual priors, both of monasteries that are members of congregations, as well as of those unaffiliated with any particular congregation. The Congress of Abbots elects the Abbot Primate, who serves a four-year term as the Confederation's representative and administrative head, although without direct jurisdiction over the individual Congregations.
The Confederation has its headquarters at Sant'Anselmo in Rome, which is the seat of the Abbot Primate and hosts the quadrennial Congress of Abbots. Sant'Anselmo is also home to the Benedictine Pontifical Athenaeum.
Communities of Benedictine nuns and Religious Sisters are joined in 61 congregations and federations that are associated with the Confederation, although they do not have full membership. In November 2001 after a consultation process with all monasteries of Benedictine women around the world, it was decided to use the name Communio Internationalis Benedictinarum (CIB) to designate all communities of Benedictine women recognized by the Abbot Primate as such and listed in the Catalogus Monasteriorum O.S.B.
The first attempt to group Benedictine monasteries into national Congregations was at the Fourth Lateran Council in 1215. Only the English Benedictine Congregation survives from this early attempt at centralization, and in historical reality even this Congregation is a 17th-century foundation although it was given juridical continuity with the medieval English Congregation by the Papal Bull "Plantata" of 1633. Primacy of honor is given to the Subiaco Cassinese Congregation, since this Congregation includes the Abbey of Monte Cassino, where St Benedict wrote his Rule and was buried (although Fleury Abbey also claims to house the remains of the founder). Founded in 1872, the Congregation has its origin in the Congregation of the Abbey of Santa Giustina, founded in Padua in 1408 by Dom Ludovico Barbo.
The Benedictines suffered badly in the anti-clerical atmosphere at the time of Napoleon and the modern Congregations were mostly founded in the 19th century when monasticism was revived. The majority are essentially national groupings, although the Subiaco Congregation (originally the Cassinese Congregation of the Primitive Observance) has from the first been truly international because of its interest in foreign mission.
Since the time of the Reformation, there have been independent Benedictine communities in the Protestant (especially Anglican) traditions which maintain official friendly relations with the Benedictine Confederation, although they are not formally linked with it or its congregations.
Throughout the Benedictine confederation and its subdivisions, independence and autonomy among communities are uniquely valued; too highly for Pope Pius XI, who complained that the largely nominal confederation was "an order without order". The basic unit has always been the individual abbey, rather than the Congregation. This explains why some houses (e.g. Monte Cassino, Subiaco, Saint Paul-outside-the-Walls (Rome), Montserrat and Pannonhalma) have unbroken histories of more than a thousand years while the Congregations to which they belong are more recent.
This balance between autonomy and belonging is one of the distinguishing features of the Benedictine Confederation, and brings with it both strengths and weaknesses. One immediate consequence is that there is often great diversity of observance even between houses of the same Congregation: in liturgy, timetable, pastoral involvement and habit.
The present Confederation of Congregations of Monasteries of the Order of Saint Benedict, officially, the "Benedictine Confederation" of monks, consists of the following congregations in the order given in the Catalogus Monasteriorum OSB (dates in brackets are those of the foundation of the congregations - Primacy of honour is given to the Cassinese Congregation, though the English Congregation is the oldest, because Monte Cassino was the original Abbey of St. Benedict himself. The older Camaldolese and Sylvestrine congregations joined the Confederation only in the mid-20th century.). The numbers in italics are the most recent number (#) of listed monks as found in the 2015 edition of the Catalogus Monasteriorum OSB.