An apostolic administrator in the Roman Catholic Church is a prelate appointed by the Pope to serve as the ordinary for an apostolic administration. An apostolic administration can either be an area that is not yet a diocese (a stable apostolic administration) or for a diocese that either has no bishop (an apostolic administrator sede vacante) or, in very rare cases, has an incapacitated bishop (apostolic administrator sede plena).
Apostolic administrators of stable administrations are equivalent in canon law with diocesan bishops, meaning they have essentially the same authority as a diocesan bishop. This type of apostolic administrator is usually the bishop of a titular see.
Administrators sede vacante or sede plena only serve in their role until a newly chosen diocesan bishop takes possession of the diocese. They are restricted by canon law in what they can do to the diocese they temporarily administer. For example, such an administrator may not sell real estate owned by the diocese. This type of administrator is commonly an auxiliary bishop of the diocese, a priest serving as the vicar general of the diocese, or the ordinary of a neighboring diocese.
Normally when a diocese falls vacant a vicar capitular/diocesan administrator is chosen locally, but the Pope, having full governmental power, can preempt this choice and name an apostolic administrator instead. Sometimes a retiring bishop is designated to be apostolic administrator until his successor takes office.
 Present cases
In August 2008, there were the following stable apostolic administrations, each administered by a bishop. Most of these are of the Roman rite, with the following exception:
- Southern Albania (established in 1939; suffragan of Tirana–Durrës), of the Albanian Byzantine Catholic Church
All others are of the Roman rite; most are in current or former communist countries.
- Atyrau in Kazakhstan, suffragan of the Metropolitan of Astana;
- Caucasus, immediately subject to the Holy See, established in 1991 for two former Soviet Republics: Georgia (the cathedral is in its capital Tbilisi) and Armenia
- Estonia, one of the Baltic Countries, established in 1924, with its cathedral in the capital Tallinn
- Kyrgyzstan, a former Soviet Republic in Central Asia, immediately subject, founded in 1997 as a mission sui juris and promoted in 2006
- Prizren, a former diocese in Kosovo (in 1969 absorbed by Skopje in the present Republic of Macedonia), restored in 2000, immediately subject
- Uzbekistan, former Soviet Republic in Central Asia, immediately subject, founded in 1997 as a mission sui juris and promoted in 2005
- Harbin in the People's Republic of China, immediately subject, established in 1935, with a cathedral, vacant since 1946
- Kinma (Kinmen and Matsu, under the control of the Republic of China (Taiwan)), established in 1968, led by the Archbishop of Taipei.
- Comoros (established in 1975; still includes Mayotte, which split off politically by remaining under French administration and even joined metropolitan France in 2011), immediately subject, administrated by a priest.
- The Diocese of Kilfenora, in the west of Ireland has had the Bishop of the neighbouring Diocese of Galway and Kilmacduagh as Apostolic Administrator since 1883. They have not been united because they are in different ecclesiastical provinces.
- The Diocese of Pensacola-Tallahassee in Florida, USA, immediately subject, after the abdication of John Ricard from the bishopric in early March 2011. His reasons for abdicating have been disputed.[clarification needed] Thomas Wenski, Archbishop of Miami, served as Diocesan Administrator for Pensacola-Tallahassee until the appointment of Gregory Parkes as Bishop March 20, 2012.
In addition, the Personal Apostolic Administration of Saint John Mary Vianney is a non-territorial jurisdiction, similar to a personal prelature. It is a separate particular church for traditionalist Catholics within the Brazilian Diocese of Campos, and suffragan of Niterói. The personal apostolic administration was formed by Pope John Paul II to administer to a group of traditionalist Catholic priests who reconciled with Rome on January 18, 2002. The group had been formed by bishop Antônio de Castro Mayer and had been associated with the Society of St. Pius X of Archbishop Marcel Lefebvre.
 See also
- Reorganization of occupied dioceses during World War II
- List of Roman Catholic dioceses (alphabetical)
- List of Roman Catholic dioceses (structured view)
- List of Roman Catholic archdioceses
- List of Roman Catholic military dioceses
- List of Roman Catholic apostolic vicariates
- List of Eastern Catholic exarchates
- List of Roman Catholic apostolic prefectures
- List of Roman Catholic territorial prelatures
- List of Roman Catholic missions sui juris
- Apostolic Administrations GCatholic.com. Accessed 2008-08-02.
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- Personal Apostolic Administrations GGatholic.com. Accessed 2008-04-10.
- Traditionalist schism in Brazil ends (January 18, 2002). Zenit News Agency. Accessed 2008-04-10.
- Apostolic Administration of São João Maria Vianney Catholic-Hierarchy.org. Accessed 2008-04-10.