Date | Country | Change |
| 1955 |  Italy | Metropolitan Archdiocese of Pisa lost territory to Archdiocese of Lucca |
| 1955 | Italy | Diocese of Pontremoli lost territory to Diocese of Luni–Sarzana |
| 1955.01.01 |  Myanmar | Diocese of Bassein was established (from Apostolic Vicariate of Rangoon and became suffragan of Rangoon) |
| 1955.01.01 | Myanmar | Apostolic Vicariate of Kengtung was promoted as Diocese of Kengtung (became suffragan of Mandalay) |
| 1955.01.01 | Myanmar | Apostolic Vicariate of Mandalay was promoted as Metropolitan Archdiocese of Mandalay (with suffragan sees Kengtung and Bhamo) |
| 1955.01.01 | Myanmar | Apostolic Vicariate of Rangoon was promoted as Metropolitan Archdiocese of Rangoon (with suffragan sees Bassein, Toungoo and Akyab and lost territory to establish Diocese of Bassein) |
| 1955.01.01 | Myanmar | Apostolic Vicariate of Toungoo was promoted as Diocese of Toungoo (became suffragan of Rangoon) |
| 1955.01.01 |  Nigeria | Apostolic Prefecture of Ogoja was promoted as Diocese of Ogoja (became suffragan of Onitsha) |
| 1955.01.01 |  Zimbabwe | Apostolic Vicariate of Bulawayo was promoted as Diocese of Bulawayo (became suffragan of Salisbury) |
| 1955.01.01 | Zimbabwe | Apostolic Vicariate of Fort Victoria was promoted as Diocese of Gwelo (became suffragan of Salisbury) |
| 1955.01.01 | Zimbabwe | Apostolic Vicariate of Salisbury was promoted as Metropolitan Archdiocese of Salisbury (with suffragan sees Bulawayo and Gwelo) |
| 1955.02.18 |  Norway,  Svalbard and Jan Mayen | Apostolic Prefecture of Northern Norway was promoted as Apostolic Vicariate of Northern Norway |
| 1955.02.21 |  Congo-Kinshasa | Apostolic Vicariate of Kwango was renamed as Apostolic Vicariate of Kikwit |
| 1955.02.21 |  Indonesia | Apostolic Vicariate of Samarinda was established (from Apostolic Vicariate of Bandjarmasin) |
| 1955.02.21 | Nigeria | Apostolic Prefecture of Kabba was established (from Diocese of Benin City, Diocese of Kaduna and Apostolic Prefecture of Oturkpo) |
| 1955.02.25 |  Finland,  Åland Islands | Apostolic Vicariate of Finland was promoted as Diocese of Helsinki (without ecclesiastical province) |
| 1955.02.25 |  Japan | Apostolic Prefecture of Kagoshima 鹿児島 was promoted as Diocese of Kagoshima 鹿児島 |
| 1955.02.25 |  Malaysia | Diocese of Kuala Lumpur was established (from Archdiocese of Malacca and became suffragan of Malacca–Singapore) |
| 1955.02.25 | Malaysia | Archdiocese of Malacca was promoted as Metropolitan Archdiocese of Malacca–Singapore (with suffragan sees Kuala Lumpur and Penang and lost territory to establish Diocese of Kuala Lumpur and Diocese of Penang) |
| 1955.02.25 | Malaysia | Diocese of Penang was established (from Archdiocese of Malacca and became suffragan of Malacca–Singapore) |
| 1955.03.06 |  Panama | Diocese of David was established (from Archdiocese of Panamá and became suffragan of Panamá) |
| 1955.03.06 | Panama | Archdiocese of Panamá was promoted as Metropolitan Archdiocese of Panamá (with suffragan see David and lost territory to establish Diocese of David) |
| 1955.03.07 |  Colombia | Diocese of Duitama was established (from Diocese of Tunja and became suffragan of Bogotá) |
| 1955.04.05 |  Brazil | Diocese of Patos de Minas was established (from Diocese of Uberaba and became suffragan of Belo Horizonte) |
| 1955.04.05 |  Philippines | Diocese of Dumaguete was established (from Diocese of Bacolod and became suffragan of Cebu) |
| 1955.04.21 |  Chile | Apostolic Administration of Copiapó was promoted as Territorial Prelature of Copiapó (became suffragan of La Serena) |
| 1955.04.29 |  Guinea-Bissau | Mission sui juris of Portuguese Guinea was promoted as Apostolic Prefecture of Portuguese Guinea |
| 1955.04.29 |  India | Diocese of Coimbatore lost territory to Diocese of Trichur |
| 1955.04.29 | India | Diocese of Kottar lost territory to Diocese of Changanacherry |
| 1955.04.29 | India | Diocese of Mangalore lost territory to Diocese of Tellicherry |
| 1955.04.29 | India | Diocese of Mysore lost territory to Diocese of Tellicherry |
| 1955.04.29 | India | Diocese of Quilon lost territory to Diocese of Changanacherry |
| 1955.04.29 | India | Diocese of Trivandrum lost territory to Diocese of Changanacherry |
| 1955.05.08 | Chile | Apostolic Prefecture of Aysén was promoted as Apostolic Vicariate of Aysén |
| 1955.05.08 | India | Diocese of Amravati was established (from Metropolitan Archdiocese of Nagpur and became suffragan of Nagpur) |
| 1955.05.08 |  Kenya | Diocese of Mombasa and Zanzibar was established (from Metropolitan Archdiocese of Nairobi and became suffragan of Nairobi) |
| 1955.05.08 |  Pakistan | Diocese of Multan lost territory to Diocese of Rawalpindi |
| 1955.05.13 | India | Diocese of Ajmer was renamed as Diocese of Ajmer–Jaipur |
| 1955.05.20 | India | Diocese of Cochin lost territory to Diocese of Trivandrum |
| 1955.06.12 | Philippines | Territorial Prelature of Bangued was established (from Metropolitan Archdiocese of Nueva Segovia and became suffragan of Nueva Segovia) |
| 1955.06.12 | Philippines | Territorial Prelature of Iba was established (from Diocese of Lingayen–Dagupan and Diocese of San Fernando and became suffragan of Manila) |
| 1955.07.03 | India | Diocese of Ootacamund was established (from Diocese of Mysore and became suffragan of Madras and Mylapore) |
| 1955.07.03 |  Peru | Apostolic Prefecture of San José de Amazonas was promoted as Apostolic Vicariate of San José de Amazonas |
| 1955.07.03 | Philippines | Apostolic Prefecture of Palawan was promoted as Apostolic Vicariate of Palawan |
| 1955.07.03 |  South Sudan | Apostolic Vicariate of Rumbek was established (from Apostolic Vicariate of Bahr el-Gebel, Apostolic Vicariate of Bahr el-Ghazal and Apostolic Prefecture of Mupoi) |
| 1955.07.12 | Brazil | Territorial Prelature of Parintins was established (from Metropolitan Archdiocese of Manaus and became suffragan of Manaus) |
| 1955.07.16 | Brazil | Diocese of Sete Lagoas was established (from Metropolitan Archdiocese of Belo Horizonte and Metropolitan Archdiocese of Diamantina and became suffragan of Belo Horizonte) |
| 1955.07.16 |  Netherlands | Diocese of Groningen was restored (from Metropolitan Archdiocese of Utrecht and Diocese of Haarlem and became suffragan of Utrecht) |
| 1955.07.16 | Netherlands | Diocese of Haarlem lost territory to Diocese of Breda |
| 1955.07.16 | Netherlands | Diocese of Rotterdam was established (from Diocese of Haarlem and became suffragan of Utrecht) |
| 1955.07.27 |  Angola | Diocese of Sá da Bandeira was established (from Diocese of Nova Lisboa) |
| 1955.08.25 |  Ecuador | Diocese of Bolivar was renamed as Diocese of Riobamba |
| 1955.09.02 |  Spain | Metropolitan Archdiocese of Burgos exchanged territory with Diocese of Osma |
| 1955.09.02 | Spain | Diocese of Calahorra y La Calzada lost territory to Diocese of Osma |
| 1955.09.02 | Spain | Diocese of Cuenca lost territory to Metropolitan Archdiocese of Toledo and Diocese of Sigüenza |
| 1955.09.02 | Spain | Diocese of Huesca lost territory to Metropolitan Archdiocese of Zaragoza and Diocese of Jaca |
| 1955.09.02 | Spain | Diocese of Lérida lost territory to Metropolitan Archdiocese of Zaragoza and Diocese of Barbastro |
| 1955.09.02 | Spain | Diocese of Osma lost territory to Diocese of Segovia |
| 1955.09.02 | Spain | Diocese of Segovia lost territory to Metropolitan Archdiocese of Valladolid |
| 1955.09.02 | Spain | Diocese of Sigüenza lost territory to Metropolitan Archdiocese of Zaragoza, Diocese of Osma, Diocese of Segovia and Diocese of Tarazona |
| 1955.09.02 | Spain | Diocese of Tarazona lost territory to Diocese of Calahorra y La Calzada, Diocese of Osma and Diocese of Pamplona |
| 1955.09.02 | Spain | Diocese of Teruel lost territory to Diocese of Cuenca, Diocese of Segorbe, Diocese of Sigüenza and Diocese of Tortosa |
| 1955.09.02 | Spain | Metropolitan Archdiocese of Toledo (Mozarabic Rite) lost territory to Diocese of Sigüenza |
| 1955.09.02 | Spain | Diocese of Tortosa lost territory to Diocese of Lérida |
| 1955.09.02 | Spain,  Andorra | Diocese of Urgell lost territory to Diocese of Barbastro |
| 1955.09.02 | Spain | Metropolitan Archdiocese of Zaragoza lost territory to Diocese of Tarazona and Diocese of Teruel |
| 1955.09.14 |  Algeria | Apostolic Vicariate of Ghardaïa nel Sahara was promoted as Diocese of Laghouat (without ecclesiastical province) |
| 1955.09.14 |  Benin | Apostolic Vicariate of Ouidah was promoted as Metropolitan Archdiocese of Cotonou (with suffragan see Porto Novo) |
| 1955.09.14 | Benin | Apostolic Vicariate of Porto Novo was promoted as Diocese of Porto Novo (became suffragan of Cotonou) |
| 1955.09.14 |  Burkina Faso | Apostolic Vicariate of Bobo-Dioulasso was promoted as Diocese of Bobo-Dioulasso (became suffragan of Ouagadougou) |
| 1955.09.14 | Burkina Faso | Apostolic Vicariate of Koudougou was promoted as Diocese of Koudougou (became suffragan of Ouagadougou) |
| 1955.09.14 | Burkina Faso | Apostolic Vicariate of Nouna was promoted as Diocese of Nouna (became suffragan of Ouagadougou) |
| 1955.09.14 | Burkina Faso | Apostolic Vicariate of Ouagadougou was promoted as Metropolitan Archdiocese of Ouagadougou (with suffragan sees Bobo-Dioulasso, Koudougou and Nouna) |
| 1955.09.14 |  Cameroon | Apostolic Vicariate of Douala was promoted as Diocese of Douala (became suffragan of Yaoundé) |
| 1955.09.14 | Cameroon | Apostolic Vicariate of Doumé was promoted as Diocese of Doumé (became suffragan of Yaoundé) |
| 1955.09.14 | Cameroon | Apostolic Vicariate of Garoua was promoted as Diocese of Garoua (became suffragan of Yaoundé) |
| 1955.09.14 | Cameroon | Apostolic Vicariate of Foumban was promoted as Diocese of Nkongsamba (became suffragan of Yaoundé) |
| 1955.09.14 | Cameroon | Apostolic Vicariate of Yaoundé was promoted as Metropolitan Archdiocese of Yaoundé (with suffragan sees Douala, Doumé, Garoua and Nkongsamba) |
| 1955.09.14 |  Central African Republic | Apostolic Vicariate of Bangui was promoted as Metropolitan Archdiocese of Bangui (with suffragan sees Berbérati and Fort-Lamy) |
| 1955.09.14 | Central African Republic | Apostolic Vicariate of Berbérati was promoted as Diocese of Berbérati (became suffragan of Bangui) |
| 1955.09.14 |  Chad | Apostolic Prefecture of Fort-Lamy was promoted as Diocese of Fort-Lamy (became suffragan of Bangui) |
| 1955.09.14 |  Congo-Brazzaville | Apostolic Vicariate of Brazzaville was promoted as Metropolitan Archdiocese of Brazzaville (with suffragan sees Fort-Rousset, Libreville and Pointe-Noire) |
| 1955.09.14 | Congo-Brazzaville | Apostolic Vicariate of Fort-Rousset was promoted as Diocese of Fort-Rousset (became suffragan of Brazzaville) |
| 1955.09.14 | Congo-Brazzaville | Apostolic Vicariate of Pointe-Noire was promoted as Diocese of Pointe-Noire (became suffragan of Brazzaville) |
| 1955.09.14 |  Cote d’Ivoire | Apostolic Vicariate of Abidjan was promoted as Metropolitan Archdiocese of Abidjan (with suffragan sees Bouaké, Daloa and Katiola) |
| 1955.09.14 | Cote d’Ivoire | Apostolic Vicariate of Bouaké was promoted as Diocese of Bouaké (became suffragan of Abidjan) |
| 1955.09.14 | Cote d’Ivoire | Apostolic Vicariate of Sassandra was promoted as Diocese of Daloa (became suffragan of Abidjan) |
| 1955.09.14 | Cote d’Ivoire | Apostolic Vicariate of Katiola was promoted as Diocese of Katiola (became suffragan of Abidjan) |
| 1955.09.14 |  Djibouti | Apostolic Prefecture of Djibouti was promoted as Diocese of Djibouti (without ecclesiastical province) |
| 1955.09.14 |  Gabon | Apostolic Vicariate of Libreville was promoted as Diocese of Libreville (became suffragan of Brazzaville) |
| 1955.09.14 |  Guinea | Apostolic Vicariate of Conakry was promoted as Metropolitan Archdiocese of Conakry |
| 1955.09.14 |  Madagascar | Apostolic Vicariate of Ambanja was promoted as Diocese of Ambanja (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Antsirabé was promoted as Diocese of Antsirabé (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Diégo-Suarez was promoted as Diocese of Diégo-Suarez (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Fianarantsoa was promoted as Diocese of Fianarantsoa (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Fort-Dauphin was promoted as Diocese of Fort-Dauphin (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Majunga was promoted as Diocese of Majunga (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Miarinarivo was promoted as Diocese of Miarinarivo (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Prefecture of Morondava was promoted as Diocese of Morondava (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Tamatave was promoted as Diocese of Tamatave (became suffragan of Tananarive) |
| 1955.09.14 | Madagascar | Apostolic Vicariate of Tananarive was promoted as Metropolitan Archdiocese of Tananarive (with suffragan sees Ambanja, Antsirabé, Diégo-Suarez, Fianarantsoa, Fort-Dauphin, Majunga, Miarinarivo, Morondava and Tamatave) |
| 1955.09.14 |  Mali | Apostolic Vicariate of Bamako was promoted as Metropolitan Archdiocese of Bamako |
| 1955.09.14 |  Morocco | Apostolic Vicariate of Rabat was promoted as Archdiocese of Rabat (without ecclesiastical province) |
| 1955.09.14 |  Senegal | Apostolic Vicariate of Dakar was promoted as Metropolitan Archdiocese of Dakar (with suffragan see Ziguinchor) |
| 1955.09.14 | Senegal | Apostolic Vicariate of Ziguinchor was promoted as Diocese of Ziguinchor (became suffragan of Dakar) |
| 1955.09.14 |  Togo | Apostolic Vicariate of Lomé was promoted as Metropolitan Archdiocese of Lomé (with suffragan see Sokodé) |
| 1955.09.14 | Togo | Apostolic Prefecture of Sokodé was promoted as Diocese of Sokodé (became suffragan of Lomé) |
| 1955.09.20 |  South Korea,  North Korea | Apostolic Prefecture of Chunchon 춘천 was promoted as Apostolic Vicariate of Chunchon 춘천 |
| 1955.09.20 |  Vietnam | Apostolic Vicariate of Cân Tho was established (from Apostolic Vicariate of Phnom Penh) |
| 1955.11.15 | Chile | Diocese of Osorno was established (from Diocese of Puerto Montt and Diocese of Valdivia and became suffragan of Concepción) |
| 1955.11.15 |  Uruguay | Diocese of Florida–Melo was renamed as Diocese of Florida (lost territory to establish Diocese of Melo) |
| 1955.11.15 | Uruguay | Diocese of Melo was restored (from Diocese of Florida–Melo and became suffragan of Montevideo) |
| 1955.11.15 | Uruguay | Diocese of San José de Mayo was established (from Metropolitan Archdiocese of Montevideo and Diocese of Salto and became suffragan of Montevideo) |
