This is a growing list of territorial dioceses and ordinariates in communion with the Holy See. There are approximately 3,000 actual (i.e., non-titular) dioceses in the Catholic Church (including the eparchies of the Eastern Catholic Churches).

Those dioceses which are (metropolitan or nominal) archdioceses (including archeparchies) are marked in bold type and are also listed at List of Catholic archdioceses. Those dioceses which belong to Eastern Catholic Churches (often called "eparchies") are italicized and their particular Churches and proper episcopal titulature are specified after the see name. Missionary and other special types of circumscriptions (e.g., apostolic prefectures) are also specified before the country name.

List of Catholic dioceses (alphabetical)

Alphabetical list of geographic dioceses

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A

Aachen (Aix-la-chapelle), Germany

Aba, Nigeria

Abaetetuba, Brazil

Abakaliki, Nigeria

Abancay, Peru

Abengourou, Côte d'Ivoire

Abeokuta, Nigeria

Aberdeen, Scotland, United Kingdom

Abidjan, Côte d'Ivoire

Abomey, Benin

Abuja, Nigeria

Acapulco, Mexico

Acarigua-Araure, Venezuela

Accra, Ghana

Acerenza, Italy

Acerra, Italy

Achonry, Ireland

Acireale, Italy

Acqui, Italy

Addis Abeba, Ethiopian Catholic Archeparchy, Ethiopia

Adelaide, Australia

Adigrat, Ethiopia

Adilabad, India

Adria-Rovigo, Italy

Afogados da Ingazeira, Brazil

Agaña, Guam

Agartala, India

Agats, Indonesia

Agboville, Côte d'Ivoire

Agen, France

Agra, India

Agrigento, Italy

Aguarico, Apostolic Vicariate, Ecuador

Aguascalientes, Mexico

Ahiara, Nigeria

Ahmedabad, India

Ahvaz (Ahwaz), Chaldean Catholic, Iran

Aiquile, Territorial Prelature, Bolivia

Aire-et-Dax, France

Aitape, Papua New Guinea

Aix-Arles-Embrun, France

Aix-la-chapelle: see Aachen

Aizawl, India

Ajaccio, France

Ajmer, India

Akka, Melkite Archeparchy, Israel

Alagoinhas, Brazil

Alajuela, Costa Rica

Alaminos, Philippines

Alba Pompeia, Italy

Alba Iulia, Romania

Albacete, Spain

Albano, Italy

Albany, United States

Albenga-Imperia, Italy

Albi, France

Alcalá de Henares, Spain

Alep (Melkite)*, Syria

Aleppo (Syrian Catholic),*, Syria

Aleppo (Maronite),*, Syria

Aleppo (Armenian),*, Syria

Aleppo, Chaldean Catholic*, Syria

Alep(po), Apostolic Vicariate (Roman Catholic), Syria

Alessandria, Italy

Ales-Terralba, Italy

Alexandria of Egypt(-Heliopolis-Port Said), Apostolic Vicariate, Egypt

Alexandria (Iskanderiya), Armenian Catholic Eparchy, Egypt

Alexandria-Cornwall, Canada

Alexandria in Louisiana, United States

Algiers, Algeria

Alghero-Bosa, Italy

Alife-Caiazzo, Italy

Alindao, Central African Republic

Aliwal, South Africa

Allahabad, India

Allentown, United States

Alleppey, India

Almenara, Brazil

Almería, Spain

Alotau-Sideia, Papua New Guinea

Alquoch, Chaldean Catholic Eparchy, Iraq

Altamura-Gravina-Acquaviva delle Fonti, Italy

Alto Solimões, Brazil

Alto Valle del Río Negro, Argentina

Altoona-Johnstown, United States

Amadiyah, Chaldean Catholic Eparchy, Iraq

Amalfi-Cava de' Tirreni, Italy

Amargosa, Brazil

Amarillo, United States

Ambanja, Madagascar

Ambato, Ecuador

Ambatondrazaka, Madagascar

Ambikapur, India

Amboina, Indonesia

Ambositra, Madagascar

Amiens, France

Amos, Canada

Amparo, Brazil

Amravati, India

Anagni-Alatri, Italy

Anápolis, Brazil

Anatolia, Apostolic Vicariate, (Asian) Turkey

Añatuya, Argentina

Anchorage, United States

Ancona-Osimo, Italy

Andong, South Korea

Andria, Italy

Aného, Togo

Angers, France

Angoulême, France

Angra, Portugal

Anking, China

Ankwo, China

Annecy, France

Annunciation of Ibadan, Maronite Catholic Eparchy, Nigeria

Anse-à-Veau and Miragoâne, Haiti

Antananarivo, Madagascar

Antélias, Lebanon

Antequera, Mexico

Antigonish, Canada

Antipolo, Philippines

Antofagasta, Chile

Antsirabe, Madagascar

Antsiranana, Madagascar

Antwerp, Belgium

Anuradhapura, Sri Lanka

List of Catholic dioceses (alphabetical)