The Diocese of Gaul (Latin: Dioecesis Galliarum, "diocese of the Gaul [province]s") is a diocese of the later Roman Empire, under the praetorian prefecture of Gaul.

It encompasses northern and eastern Gaul, that is, modern France north and east of the Loire, including the Low Countries and modern Germany west of the Rhine.The diocese comprises the following provinces: Gallia Lugdunensis I, Gallia Lugdunensis II, Gallia Lugdunensis III, Gallia Lugdunensis IV (Senonia), Belgica I, Belgica II, Germania I, Germania II, Alpes Poenninae et Graiae and Maxima Sequanorum.