| Date | Country | Change |
| 1825 | Diocese of Agrigento lost territory to Metropolitan Archdiocese of Palermo | |
| 1825 | Diocese of Cefalù lost territory to Metropolitan Archdiocese of Palermo | |
| 1825 | Diocese of Huamanga was renamed as Diocese of Ayacucho | |
| 1825.08.05 | Diocese of Tarentaise was restored (from Metropolitan Archdiocese of Chambéry and became suffragan of Chambéry) | |
| 1825.08.07 | Diocese of Saint-Jean-de-Maurienne was restored (from Metropolitan Archdiocese of Chambéry and became suffragan of Chambéry) | |
| 1825.08.19 | Apostolic Vicariate of Mississippi was restored (from Diocese of Louisiana and the Two Floridas) | |
| 1825.08.29 | Apostolic Vicariate of Alabama and the Floridas was established (from Metropolitan Archdiocese of Baltimore and Diocese of Louisiana and the Two Floridas) | |
| 1825.08.29 | Diocese of Louisiana and the Two Floridas was renamed as Diocese of Louisiana (lost territory to establish Apostolic Vicariate of Alabama and the Floridas) | |
| 1825.11.27 | Apostolic Prefecture of Sandwich Islands was established | |
| 1825.12.10 | Diocese of Civitavecchia was restored (from Diocese of Tuscanella) |
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