The Diocese of Vannes is a Roman Catholic diocese located in the region of Brittany, France. It was established in the 5th century and is part of the ecclesiastical province of Rennes. The diocese covers the area around the city of Vannes and includes several surrounding towns and villages. The diocese is known for its rich history and cultural heritage, including numerous churches and religious sites. The Cathedral of Saint Peter in Vannes serves as the seat of the bishop and is an important landmark. The diocese plays a significant role in the spiritual life of the local community.