| Date | From | To |
|---|
| 4th Century | | | Diocese of Agen, France
| Erected |
| 4th Century | | | Diocese of Alba, Italy
| Erected |
| 4th Century | | | Diocese of Acqui, Italy
| Erected |
| 4th Century | | | Diocese of Ascoli Piceno, Italy
| Erected |
| 4th Century | | | Diocese of Barcelona, Spain
| Erected |
| 4th Century | | | Diocese of Bari, Italy
| Erected |
| 4th Century | | | Diocese of Bayonne, France ((or 6th Century))
| Erected |
| 4th Century | Diocese of Besançon, France
| Elevated | Archdiocese of Besançon, France
| Elevated |
| 4th Century | | | Diocese of Bergamo, Italy
| Erected |
| 4th Century | | | Diocese of Braga, Portugal
| Erected |
| 4th Century | | | Diocese of Brindisi, Italy
| Erected |
| 4th Century | | | Diocese of Cagliari, Italy
| Erected |
| 4th Century | | | Diocese of Squillace, Italy
| Erected |
| 4th Century | | | Diocese of Sarsina, Italy
| Erected |
| 4th Century | | | Diocese of Concordia, Italy
| Erected |
| 4th Century | | | Diocese of Como, Italy
| Erected |
| 4th Century | | | Diocese of Cremona, Italy
| Erected |
| 4th Century | | | Diocese of Cagli, Italy
| Erected |
| 4th Century | | | Diocese of Digne, France
| Erected |
| 4th Century | | | Diocese of Évora, Portugal
| Erected |
| 4th Century | | | Diocese of Ferrara, Italy
| Erected |
| 4th Century | | | Diocese of Ferentino, Italy
| Erected |
| 4th Century | | | Diocese of Gerona, Spain
| Erected |
| 4th Century | | | Diocese of Piacenza, Italy
| Erected |
| 4th Century | | | Diocese of Grenoble, France
| Erected |
| 4th Century | | | Diocese of Imola, Italy
| Erected |
| 4th Century | | | Diocese of Genève, Switzerland
| Erected |
| 4th Century | | | Diocese of León, Spain
| Erected |
| 4th Century | | | Diocese of Liège, Belgium
| Erected |
| 4th Century | | | Diocese of Lisboa, Portugal
| Erected |
| 4th Century | | | Diocese of Lodi, Italy
| Erected |
| 4th Century | | | Diocese of Lucera, Italy
| Erected |
| 4th Century | | | Diocese of Mainz, Germany
| Erected |
| 4th Century | Diocese of Milano, Italy
| Elevated | Archdiocese of Milano {Milan}, Italy
| Elevated |
| 4th Century | | | Diocese of Nantes, France
| Erected |
| 4th Century | | | Diocese of Novara, Italy
| Erected |
| 4th Century | | | Suburbicarian See of Palestrina, Italy
| Erected |
| 4th Century | | | Diocese of Parma, Italy
| Erected |
| 4th Century | | | Diocese of Pisa, Italy
| Erected |
| 4th Century | | | Diocese of Porto, Portugal
| Erected |
| 4th Century | | | Diocese of Marsico Nuovo, Italy
| Erected |
| 4th Century | Diocese of Sevilla, Spain
| Elevated | Archdiocese of Sevilla {Seville}, Spain
| Elevated |
| 4th Century | | | Suburbicarian See of Albano, Italy
| Erected |
| 4th Century | | | Archdiocese of Dardania, Macedonia
| Erected |
| 4th Century | | | Diocese of Siena, Italy
| Erected |
| 4th Century | | | Diocese of Sion {Sitten}, Switzerland
| Erected |
| 4th Century | | | Diocese of Castellammare di Stabia, Italy
| Erected |
| 4th Century | | | Diocese of Speyer, Germany
| Erected |
| 4th Century | | | Diocese of Strasbourg, France
| Erected |
| 4th Century | | | Diocese of Narni, Italy
| Erected |
| 4th Century | | | Diocese of Tempio, Italy
| Erected |
| 4th Century | Diocese of Toledo, Spain
| Elevated | Archdiocese of Toledo, Spain
| Elevated |
| 4th Century | | | Diocese of Torino, Italy
| Erected |
| 4th Century | | | Diocese of Tortosa, Spain
| Erected |
| 4th Century | | | Diocese of Treviso, Italy
| Erected |
| 4th Century | | | Diocese of Troyes, France
| Erected |
| 4th Century | | | Diocese of Urgell, Spain
| Erected |
| 4th Century | | | Diocese of Valence, France
| Erected |
| 4th Century | | | Diocese of Acerenza, Italy
| Erected |
| 4th Century | | | Eparchy of Alep (Melkite), Syria
| Erected |
| 4th Century | | | Diocese of Avignon, France
| Erected |
| 4th Century | | | Diocese of Sirmio, Croatia
| Erected |
| 4th Century | | | Confederation of Canons Regular of St. Augustine
| Founded |
| 4th Century | | | Cardinal Titular Church of Albano
| Erected |
| 4th Century | | | Cardinal Titular Church of Palestrina
| Erected |
| 4th Century | | | Cardinal Titular Church of S. Cecilia
| Established |
| 4th Century | | | Diocese of Antibes, France
| Erected |
| 4th Century | | | Diocese of Apt, France
| Erected |
| 4th Century | | | Diocese of Chalons-sur-Marne, France
| Erected |
| 4th Century | | | Diocese of Cimiez, France
| Erected |
| 4th Century | | | Diocese of Couserans, France
| Erected |
| 4th Century | | | Diocese of Embrun, France
| Erected |
| 4th Century | | | Diocese of Fréjus, France
| Erected |
| 4th Century | | | Diocese of Lectoure, France
| Erected |
| 4th Century | | | Diocese of Nevers, France
| Erected |
| 4th Century | Diocese of Reims, France
| Elevated | Archdiocese of Reims, France
| Elevated |
| 4th Century | | | Diocese of Saint-Paul-Trois-Châteaux, France
| Erected |
| 4th Century | | | Diocese of Tarbes, France
| Erected |
| 4th Century | | | Diocese of Verdun, France
| Erected |
| 4th Century | | | Diocese of Vernay, France
| Erected |
| 4th Century | | | Diocese of Viviers (Aps), France
| Erected |
