The Diocese of Lille is a Roman Catholic diocese located in northern France. It was established in the 11th century and is part of the Province of Reims. The diocese serves the spiritual needs of the Catholic community in the region, overseeing various parishes and religious institutions. The cathedral of the diocese is the Basilique-cathédrale Notre-Dame de la Treille, which is known for its unique architectural style that combines modern and traditional elements. The diocese also engages in various social and educational initiatives to support the local community and promote the Catholic faith.