A co-cathedral is a cathedral church which shares the function of being a bishop's seat, or cathedra, with another cathedral, often in another city (usually a former see, anchor city of the metropolitan area or the civil capital). Instances of this occurred in England before the Protestant Reformation in the dioceses of 'Bath and Wells', and of 'Coventry and Lichfield'. These two dioceses were each named for both cities that served as bishop's seats.
As of March 2020, the Catholic Church had 322 co-cathedrals, mainly in Europe (140 in Italy alone).
Many are former cathedrals and mother churches, but even if still in use, those often are not granted co-cathedral status.
Often the diocese with one or more co-cathedrals also has a multiple ("hyphenated") name reflecting these, but some have a co-cathedral not mentioned in the title while other former see titles may also be preserved without having a co-cathedral. Sometimes the first-named city does not have the main cathedral (actual see) but boasts another distinction such as being a national capital or having an august ecclesiastical past.
Catholic Europe
Albania In Albania, the Roman Catholic Archdiocese of Tirana-Durrës has a co-cathedral in Durrës, Saint Lucia co-cathedral.
Belgium
In Belgium, the cathedral of the primatial Roman Catholic Archdiocese of Mechelen-Brussels is the Metropolitan St. Rumbold's Cathedral in Mechelen (Malines), the archiepiscopal seat. Its co-cathedral is the Cathedral of St. Michael and St. Gudula in Brussels, the national capital. A third, larger church in Koekelberg (also in Brussels) has the status of minor basilica, without co-cathedral rank, yet it has received papal visits including a papal beatification.
Bulgaria The Roman Catholic Diocese of Sofia and Plovdiv has, besides the Cathedral of St Louis in Plovdiv, a new co-cathedral of St. Joseph in Sofia.
Croatia
The Metropolitan archbishop of Split-Makarska has, in Split (Dalmatia), the co-cathedral of Saint Peter the Apostle Konkatedrala sv. Petra Apostola, besides his episcopal see, Katedrala Sv. Dujma The Metropolitan archbishop of Đakovo-Osijek has, in Osijek (Slavonia), the co-cathedral of St Peter and St Paul Crkva svetog Petra i Pavla, besides his episcopal see, Katedrala Bazilika Svetog Petra
Czech Republic The Roman Catholic Diocese of Ostrava-Opava has a co-cathedral of Our Lady of the Assumption Co-Cathedral in Ostravian-Opavian diocese in Opava besides the Ostrava Savior cathedral.
France The double-titled bishopric of Aire and Dax has a Co-cathedral of Notre Dame in Dax and a Cathedral of St John the Baptist in Aire The Archdiocese of Chambéry–Saint-Jean-de-Maurienne–Tarentaise has its cathedral in Chambéry and co–cathedrals in Saint-Jean-de-Maurienne and in Tarentaise The bishop of Couserans (a see suppressed in the French Revolution) had two co-cathedral churches at Saint-Lizier The bishop of Sisteron (a see also suppressed) had a second throne in the church of Forcalquier, which is still called La Con-cathédrale.
Germany The Roman Catholic Diocese of Augsburg has a co-cathedral of Saints Peter and Paul in Dillingen and a cathedral of the Visitation of Holy Mary in Augsburg The Roman Catholic Diocese of Dresden-Meissen has a co-cathedral of Saint Peter in Bautzen and a cathedral of the Most Holy Trinity in Dresden The Roman Catholic Archdiocese of Munich and Freising has a co-cathedral of Saints Mary and Korbinian in Freising and a cathedral of Our Dear Lady in Munich The Roman Catholic Diocese of Rottenburg-Stuttgart has a co-cathedral of Saint Eberhard in Stuttgart and a cathedral of Saint Martin in Rottenburg am Neckar.
Hungary The primatial Metropolitan see of the Roman Catholic Archdiocese of Esztergom-Budapest has its primary cathedral in the old archiepiscopal seat, the Cathedral Basilica of Esztergom, and a co-cathedral basilica in the national state capital Budapest.
Italy
The Diocese of Adria-Rovigo has a Concattedrale di S. Stefano Papa e Martire Concattedrale dedicated to Martyr Pope Stephen I in Rovigo, which never was a diocese, besides Adria's own Cattedrale di SS. Pietro e Paolo dedicated to Saints Peter and Paul The Diocese of Alghero-Bosa has a Marian co-Cathedral Concattedrale di Beata Vergine Immacolata Concattedrale di Beata Vergine Immacolata, in Bosa besides its cathedral episcopal see, the Marian Cattedrale di Beata Maria Vergine Immacolata Concezione, in Alghero The Diocese of Amalfi-Cava de' Tirreni has a Marian co-cathedral of the Visitation of Mary in Cava de' Tirreni, besides the cathedral of Apostle Andrew in Amalfi. The Diocese of Avezzano has its cathedral in that city and a co-cathedral in its former see Pescina The Diocese of Bolzano-Brixen has its cathedral in Brixen and a co-cathedral in Bolzano The Archdiocese of Campobasso-Boiano has a cathedral in and a co-cathedral in . The Diocese of Lucera-Troia has its cathedral in Lucera, present see; Troia's former cathedral serves as co-cathedral The Diocese of Melfi-Rapolla-Venosa has a cathedral, a Marian Minor Basilica: Basilica Cattedrale di S. Maria Assunta, in Melfi, and two co-cathedrals: Concattedrale di S. Andrea in Venosa, and Concattedrale di S. Michele Arcangelo, in Rapolla The Diocese of Molfetta-Ruvo-Giovinazzo-Terlizzi has a cathedral in Molfetta and three co-cathedrals in Ruvo, Giovinazzo and Terlizzi The Diocese of Pitigliano-Sovana-Orbetello has a cathedral of Peter&Paul in Pitigliano and a co-cathedral of the Assumptio in Orbetello The Archdiocese of Rossano-Cariati has a Marian cathedral di Maria SS. Achiropita at Rossano and a co-cathedral of the Archangel Michael in Cariati The Archdiocese of Sant'Angelo dei Lombardi-Conza-Nusco-Bisaccia has its cathedral in Sant'Angelo dei Lombardi and three co-cathedrals in absorbed former bishoprics: Conza della Campania, Nusco and Bisaccia The Diocese of Sora-Cassino-Aquino-Pontecorvo has the cathedral of St. Mary of the Assumption in Sora, the co-cathedral of the Holy Savior, St. Mary of the Assumption, and Saint Germanus Bishop in Cassino; the co-cathedral of the Saints Constantius Bishop and Martyr and Thomas Aquinas in Aquino; and the co-cathedral of St. Bartholomew the Apostle in Pontecorvo The Diocese of Teggiano-Policastro has a co-cathedral of the Assumption in Policastro Bussentino and a Marian cathedral of S. Maria Maggiore e S. Michele Arcangelo in Teggiano The Diocese of Termoli-Larino has its cathedral in Termoli and a co-cathedral in Larino
Malta
The metropolitan cathedral of the Roman Catholic Archdiocese of Malta is St. Paul's Cathedral in the former capital Mdina. Since the 1820s, the former Conventual Church of St. John in Valletta has been known as St. John's Co-Cathedral.
Netherlands
Since 8 March 2025, the Basilica of Saint Nicholas, Amsterdam, is co-cathedral with the Cathedral of St Bavo, Haarlem.
Poland the Roman Catholic Diocese of Zamość-Lubaczów has a cathedral of the Resurrection and St. Thomas the Apostle in Zamość and a co-cathedral of St. Stanislaus in Lubaczów The Roman Catholic Archdiocese of Szczecin-Kamień has a cathedral of James the Elder in Szczecin and a co-cathedral of John the Baptist in Kamień; the same goes for both its suffragans : the Roman Catholic Diocese of Zielona Góra-Gorzów has a cathedral of the Virgin Mary in Gorzów and a co-cathedral of St. Jadwiga in Zielona Góra The Roman Catholic Diocese of Koszalin-Kołobrzeg has a cathedral in Koszalin and a co-cathedral in Kołobrzeg
Slovakia Co-Cathedral of St. Nicholas, Prešov Co-Cathedral of Our Lady of Sorrows, Poprad
Slovenia The Diocese of Koper has a Co-cathedral of Christ the Saviour in Nova Gorica besides its Cathedral of the Assumption of the Blessed Virgin Mary in Koper
Spain The Diocese of Calahorra y La Calzada-Logroño has a Co-Cathedral of St Mary in Logroño besides its Cathedral of the Assumption of Our Lady in Calahorra and Cathedral of the Saviour and St Mary of Santo Domingo de la Calzada. The Diocese of Coria-Cáceres has a Co-Cathedral of St Mary in Cáceres besides its Cathedral of the Assumption of Our Lady in Coria. The Diocese of Guadix-Baza has a Co-Cathedral of Our Lady of the Incarnation (es) in Baza besides its Cathedral of the Incarnation in Guadix. The Archdiocese of Mérida-Badajoz has a Co-Cathedral of Saint Mary Major in Mérida besides its Cathedral of St John the Baptist in Badajoz. The Diocese of Mondoñedo-Ferrol has a Co-Cathedral of St Martin in Ferrol beside its Cathedral Basilica of the Assumption of Our Lady in Mondoñedo. The Diocese of Orihuela-Alicante has a Co-Catedral of St Nicholas of Bary in Alicante besides its Cathedral of the Saviour and St Mary in Orihuela. The Diocese of Osma-Soria has a Co-Cathedral of St Peter in Soria besides its Cathedral of the Assumption of Our Lady in Burgo de Osma. The Diocese of Segorbe-Castellón has a Co-Cathedral os St Mary in Castellón de la Plana besides its Cathedral of the Assumption of Our Lady in Segorbe. The Diocese of Sigüenza-Guadalajara has a Co-Cathedral of Santa María de la Fuente la Mayor in Guadalajara besides its Cathedral of St Mary in Sigüenza. The Diocese of Tui-Vigo has a Co-Cathedral of St Mary in Vigo besides its Cathedral of St Mary in Tui.
Ukraine Latin Diocese of Kyiv-Zhytomyr has a Co-Cathedral of St. Alexander, Kyiv, besides the Cathedral of St. Sophia, in Zhytomyr. Latin diocese of Kharkiv-Zaporizhzhia has a Co-Cathedral of the Merciful Father, Zaporizhzhia, besides the Cathedral of the Blessed Virgin Mary in Kharkiv The Roman Catholic Diocese of Odesa-Simferopol plans a co-cathedral in Simferopol, on Crimea, besides its Odesa cathedral, but suspended building plans after the Russian annexation
Catholic Asia
Indonesia The Diocese of Sibolga has a co-Cathedral named The Lady of All Nations in Gunungsitoli, Nias, besides the Cathedral of Therese of Lisieux in Sibolga.
India The Diocese of Simla and Chandigarh has a co-Cathedral, Christ the King Cathedral, at Chandigarh, which never was a diocese, besides the cathedral episcopal see of St. Michael and St. Joseph in Shimla, the capital of Himachal Pradesh state. After the merger of the ecclesiastical provinces of Madras and Mylapore in 1952 to form the Archdiocese of Madras-Mylapore. The cathedral of the former Mylapore province was given Co-cathedral standard and is now known as St Mary's Co-Cathedral.
Israel The Latin Patriarchate of Jerusalem, whose main cathedral is the Church of the Holy Sepulchre, also has a co-cathedral, namely the co-Cathedral of the Most Holy Name of Jesus.
Japan
The co-Cathedral The Basilica of the Twenty-Six Holy Martyrs of Japan, in Nagasaki also known as Ōura Cathedral, a World Heritage Site, and the oldest church in Japan. Nearby is the Immaculate Conception Cathedral, also known as Urakami Cathedral.
Korea
The Archdiocese of Daegu has, besides the Kyesan Cathedral, a new co-cathedral, Beomeo Cathedral. The Diocese of Suwon has a cathedral of Korean Martyrs in Jeongjadong and a co-cathedral of Queen of Peace in Jowon-dong
Philippines The Archdiocese of Lingayen-Dagupan has a cathedral in Dagupan, Pangasinan and the original cathedral, now co-cathedral, the Epiphany of Our Lord Parish Church in Lingayen.
Syria The Melkite Greek Catholic Archeparchy of Homs has in Yabrud (one of the two former eparchs which were title united with the diocese) the co-cathedral of Saints Constantine and Helen, besides its Cathedral of Our Lady of Peace in Homs.
Asian Turkey The Apostolic Vicariate of Anatolia has a Co-Cathedral of St. Anthony of Padua, in Mersin, besides the Marian episcopal see Cathedral of the Annunciation, in İskenderun (Alexandretta).
Catholic Africa
Egypt