Date | Country | Change |
| 1855 |  India | Mission sui juris of Central Bengal was established (from Apostolic Vicariate of Western Bengal) |
| 1855 |  Italy | Diocese of Luni–Sarzana lost territory to Diocese of Pontremoli |
| 1855.02.21 |  Canada | Diocese of London was established (from Diocese of Toronto and became suffragan of Québec) |
| 1855.05.29 | Italy | Abbacy nullius of San Pietro di Novalesa was suppressed (to Diocese of Susa) |
| 1855.06.25 | Italy | Diocese of Foggia was established (from Metropolitan Archdiocese of Manfredonia and Diocese of Troia and without ecclesiastical province) |
| 1855.06.30 |  France | Diocese of Laval was established (from Diocese of Angers and Diocese of Le Mans and became suffragan of Tours) |
| 1855.08.01 | Italy | Diocese of Brugnato lost territory to Diocese of Pontremoli |
| 1855.08.22 | Italy | Diocese of Modena was promoted as Metropolitan Archdiocese of Modena (with suffragan sees Borgo San Donnino, Carpi, Guastalla, Massa Carrara and Reggio Emilia) |
| 1855.09.04 |  Malaysia | Apostolic Prefecture of Labuan and Borneo was established (from Apostolic Vicariate of Batavia) |
| 1855.10.10 |  Equatorial Guinea | Apostolic Prefecture of Annobon, Corisco and Fernando Poo Islands was established (from Apostolic Vicariate of Deux Guinées et Sénégambie) |
| 1855.12.08 |  Norway, Canada,  Denmark,  Faroe Islands,  Greenland,  Iceland,  Scotland,  Sweden | Apostolic Prefecture of North Pole was established (from Metropolitan Archdiocese of Québec, Diocese of Saint-Boniface, Apostolic Vicariate of Nordic Missions and Apostolic Vicariate of Sweden) |
