The Roman Catholic Diocese of Laval (Latin: Dioecesis Valleguidonensis; French: Diocèse de Laval) is a Roman Catholic Latin Rite diocese in France. The episcopal see is Laval Cathedral in the city of Laval. Created in June 1855, the diocese was originally erected from the Diocese of Le Mans, and corresponds to the department of Mayenne. Under the Ancien Régime the diocese of Mans had an Archdeacon of Laval, whose responsibilities extended over the deaneries of Ernée, Évrun, Laval and Mayenne. The diocese is a suffragan of the Archdiocese of Rennes, Dol, and Saint-Malo.