Suburbicarian diocese

The seven suburbicarian dioceses are Roman Catholic dioceses located in the vicinity of Rome, whose (titular) bishops are the (now six) ordinary members of the highest-ranking order of Cardinals, the Cardinal Bishops (to which the Cardinal-patriarchs were added).

The suburbicarian dioceses have varied slightly over time and nowadays consist of:

The see of Ostia is conferred on the Dean of the College of Cardinals in addition to the see he already had. (Until 1914, the Dean received the see of Ostia and Velletri in place of the see he had earlier. The sees of Ostia and Velletri were separated in 1914.) The Cardinal-Dean used to be the longest-serving cardinal bishop, but is now chosen by the six cardinal bishops with the approval of the Pope.

The increasing involvement of the Cardinal bishops in the administration of the papal curia resulted in a detachment from their dioceses. Therefore, some of them, in particular the Cardinal-bishops of Sabina and Velletri, have for centuries had Auxiliary bishops and in 1910 Pope Pius X's apostolic constitution Apostolicae Romanorum made this practice obligatory for all suburbicarian dioceses.

In 1962, Pope John XXIII in his decree Suburbicarii Sedis turned the Cardinal bishops into merely titular bishops and appointed separate residential diocesan bishops for Velletri-Segni, Porto-Santa-Rufina, Frascati, Palestrina, Albano and Sabina. For the diocese of Ostia — the titular diocese of the Dean of the College of Cardinals — no resident diocesan bishop was appointed; it is entrusted to an apostolic administrator, which is always the Cardinal Vicar of Rome. Though the diocesan bishops exercise all episcopal administrative functions, the Cardinal bishops still formally take possession of their titular dioceses.

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