Suburbicarian diocese

The seven suburbicarian dioceses are Catholic dioceses located in the vicinity of Rome, whose bishops are the ordinary members of the highest-ranking order of cardinals, the cardinal bishops. Pope Francis had, in addition, co-opted five cardinals of the Latin Church to join the ranks of the cardinal bishops.
Being awarded the titular title of a suburbicarian see is considered more an honor or prestige than aimed towards a functional intent.

Seven suburbicarian sees

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

See	Cathedral	Incumbent	Appointed
Ostia	Santa Aurea	Giovanni Battista Re	2020
Sabina–Poggio Mirteto	Poggio Mirteto Cathedral	Giovanni Battista Re	2002
Velletri–Segni	Velletri Cathedral	Francis Arinze	2005
Porto–Santa Rufina	Cattedrale dei Sacri Cuori di Gesù e Maria	Beniamino Stella	2020
Frascati–Tusculum	Frascati Cathedral	Tarcisio Bertone	2008
Palestrina–Praeneste	Palestrina Cathedral	José Saraiva Martins	2009
Albano	Albano Cathedral	Luis Antonio Tagle	2025

The see of Ostia is conferred on the Dean of the College of Cardinals in addition to the see he already had. 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 made the cardinal bishops into titular bishops and made provision for the appointment of 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.