The Diocese of Troyes is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Troyes, France. The diocese now comprises the département of Aube. Erected in the 4th century, the diocese is currently a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Reims. It was re-established in 1802 as a suffragan of the Archbishopric of Paris, when it comprised the départements of Aube and Yonne and its bishop had the titles of Troyes, Auxerre, and Châlons-sur-Marne. In 1822, the See of Châlons was created and the Bishop of Troyes lost that title. When Sens was made an archdiocese, the episcopal title of Auxerre went to it and Troyes lost also the département of Yonne, which became the Archdiocese of Sens. The Diocese of Troyes covers, besides the ancient diocesan limits, 116 parishes of the ancient Diocese of Langres and 20 belonging to the ancient diocese of Sens. On 8 December 2002, the Diocese of Troyes was returned to its ancient metropolitan, the Archbishop of Reims. As of 2022, there was one priest for every 4,320 Catholics.