Date | Country | Change |
| 1850 |  Greece | Titular Episcopal See of Pharsalus was promoted as Titular Archiepiscopal See of Pharsalus |
| 1850 |  Iraq | Diocese of Aqrā (Chaldean Rite) was established (from Diocese of Amadiyah) |
| 1850 | Iraq | Diocese of Zaku (Chaldean Rite) was established (from Diocese of Amadiyah and Diocese of Gazireh) |
| 1850 |  Italy | Diocese of Civita Castellana lost territory to Diocese of Viterbo |
| 1850 |  Syria | Diocese of Hama (Syriac Rite) was suppressed (to Metropolitan Archdiocese of Homs and united to Metropolitan Archdiocese of Homs) |
| 1850 | Syria | Diocese of Nabk (Syriac Rite) was suppressed (to Metropolitan Archdiocese of Homs and united to Metropolitan Archdiocese of Homs) |
| 1850 |  Turkiye | Diocese of Artvin (Armenian Rite) was established |
| 1850 | Turkiye | Diocese of Cesarea in Cappadocia (Armenian Rite) was established |
| 1850 | Turkiye | Diocese of Prusa (Armenian Rite) was established |
| 1850 | Turkiye | Diocese of Trapezus (Armenian Rite) was established |
| 1850.02.15 |  Bangladesh | Apostolic Vicariate of Eastern Bengal was established (from Apostolic Vicariate of Bengal) |
| 1850.02.15 |  India | Apostolic Vicariate of Bengal was renamed as Apostolic Vicariate of Western Bengal (lost territory to Apostolic Vicariate of Lhassa 拉薩 and lost territory to establish Apostolic Vicariate of Eastern Bengal) |
| 1850.02.28 |  Costa Rica | Diocese of San José was established (from Diocese of León and became suffragan of Guatemala) |
| 1850.04.03 | India | Apostolic Pro-Vicariate of Coimbatore was promoted as Apostolic Vicariate of Coimbatore (gained territory from Apostolic Vicariate of Pondicherry) |
| 1850.04.03 | India | Apostolic Pro-Vicariate of Mysore was promoted as Apostolic Vicariate of Mysore |
| 1850.04.03 | India | Apostolic Vicariate of Pondicherry lost territory to Apostolic Vicariate of Coimbatore |
| 1850.04.03 | India | Apostolic Pro-Vicariate of Vizagapatam was promoted as Apostolic Vicariate of Vizagapatam |
| 1850.04.30 |  Dominica | Diocese of Roseau was established (from Apostolic Vicariate of Trinidad and became suffragan of Port of Spain) |
| 1850.04.30 |  Iran | Diocese of Ispahan (Armenian Rite) was established (became suffragan of Cilicia) |
| 1850.04.30 |  Trinidad and Tobago | Apostolic Vicariate of Trinidad was promoted as Metropolitan Archdiocese of Port of Spain (with suffragan see Roseau and lost territory to establish Diocese of Roseau) |
| 1850.04.30 | Turkiye | Diocese of Ancyra (Armenian Rite) was restored |
| 1850.04.30 | Turkiye | Diocese of Garin (Armenian Rite) was established |
| 1850.05.31 |  USA | Diocese of Nesqually was established (from Diocese of Walla Walla and became suffragan of Oregon City) |
| 1850.07.03 | USA | Diocese of Savannah was established (from Diocese of Charleston and Diocese of Mobile and became suffragan of Baltimore) |
| 1850.07.07 | Italy | Diocese of Modigliana was established (from Diocese of Bertinoro, Diocese of Faenza, Diocese of Forlì and Diocese of Sarsina and became suffragan of Bologna) |
| 1850.07.19 | USA | Diocese of Cincinnati was promoted as Metropolitan Archdiocese of Cincinnati (with suffragan sees Cleveland, Detroit, Louisville, Nashville and Vincennes) |
| 1850.07.19 | USA | Apostolic Vicariate of Indian Territory East of the Rocky Mountains was established (from Diocese of New Orleans) |
| 1850.07.19 | USA | Diocese of New Orleans was promoted as Metropolitan Archdiocese of New Orleans (with suffragan sees Galveston, Little Rock, Mobile and Natchez and lost territory to establish Apostolic Vicariate of Indian Territory East of the Rocky Mountains) |
| 1850.07.19 | USA | Diocese of New York was promoted as Metropolitan Archdiocese of New York (with suffragan sees Albany, Boston, Buffalo and Hartford) |
| 1850.07.19 | USA | Diocese of Saint Paul was established (from Diocese of Dubuque and Diocese of Milwaukee and became suffragan of Saint Louis) |
| 1850.07.19 | USA | Diocese of Wheeling was established (from Diocese of Richmond and became suffragan of Baltimore) |
| 1850.07.23 | USA | Apostolic Vicariate of New Mexico was established (from Diocese of Durango) |
| 1850.08.20 |  Samoa | Apostolic Vicariate of Archipelago of the Navigators was established (from Apostolic Vicariate of Central Oceania) |
| 1850.08.27 |  Vietnam | Apostolic Vicariate of Northern Cochin was established (from Apostolic Vicariate of Eastern Cochin) |
| 1850.08.30 |  Cambodia | Apostolic Vicariate of Cambodia was established (from Apostolic Vicariate of Western Cochin) |
| 1850.09.05 | Italy | Diocese of Sutri lost territory to Diocese of Civitavecchia |
| 1850.09.21 | Italy | Diocese of Capaccio–Diano was renamed as Diocese of Capaccio (lost territory to establish Diocese of Diano–Teggiano) |
| 1850.09.21 | Italy | Diocese of Diano–Teggiano was established (from Metropolitan Archdiocese of Salerno, Diocese of Capaccio–Diano and Diocese of Cava and became suffragan of Salerno) |
| 1850.09.27 |  Guadeloupe,  Saint Barthélemy,  Saint Martin | Diocese of Guadeloupe et Basse-Terre was established (from Apostolic Prefecture of Îles de la Terre Ferme and became suffragan of Bordeaux) |
| 1850.09.27 |  Martinique | Apostolic Prefecture of Îles de la Terre Ferme was promoted as Diocese of Martinique (lost territory to establish Diocese of Guadeloupe et Basse-Terre and became suffragan of Bordeaux) |
| 1850.09.27 |  Réunion | Apostolic Prefecture of Bourbon was promoted as Diocese of Saint-Denis-de-La Réunion (became suffragan of Bordeaux) |
| 1850.09.29 |  England | Apostolic Vicariate of Yorkshire District was promoted as Diocese of Beverley (became suffragan of Westminster) |
| 1850.09.29 | England | Apostolic Vicariate of Central District was promoted as Diocese of Birmingham (lost territory to establish Diocese of Nottingham and Diocese of Shrewsbury and became suffragan of Westminster) |
| 1850.09.29 | England | Apostolic Vicariate of Western District was promoted as Diocese of Clifton (lost territory to establish Diocese of Plymouth and became suffragan of Westminster) |
| 1850.09.29 | England | Apostolic Vicariate of Northern District was promoted as Diocese of Hexham (became suffragan of Westminster) |
| 1850.09.29 | England,  Isle of Man | Apostolic Vicariate of Lancashire District was promoted as Diocese of Liverpool (lost territory to establish Diocese of Salford and Diocese of Shrewsbury and became suffragan of Westminster) |
| 1850.09.29 | England | Apostolic Vicariate of Wales District was promoted as Diocese of Newport and Menevia (lost territory to establish Diocese of Shrewsbury and became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Eastern District was renamed as Diocese of Northampton (became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Nottingham was established (from Apostolic Vicariate of Central District and became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Plymouth was established (from Apostolic Vicariate of Western District and became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Salford was established (from Apostolic Vicariate of Lancashire District and became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Shrewsbury was established (from Apostolic Vicariate of Central District, Apostolic Vicariate of Lancashire District and Apostolic Vicariate of Wales District and became suffragan of Westminster) |
| 1850.09.29 | England | Diocese of Southwark was established (from Apostolic Vicariate of London District and became suffragan of Westminster) |
| 1850.09.29 | England | Apostolic Vicariate of London District was promoted as Metropolitan Archdiocese of Westminster (with suffragan sees Beverley, Birmingham, Clifton, Hexham, Liverpool, Newport and Menevia, Northampton, Nottingham, Plymouth, Salford, Shrewsbury and Southwark and lost territory to establish Diocese of Southwark) |
| 1850.11.15 |  South Africa | Apostolic Vicariate of Natal was established (from Apostolic Vicariate of Cape of Good Hope, Eastern District) |
| 1850.11.24 |  Ireland | Diocese of Cloyne and Ross was renamed as Diocese of Cloyne (lost territory to establish Diocese of Ross) |
| 1850.11.24 | Ireland | Diocese of Ross was restored (from Diocese of Cloyne and Ross) |
