the chef-lieu de département, the commune in which the administration of a department is located;
the chef-lieu de région, the commune in which the administration of a region is located;
the jurisdiction of a prefecture;
the official residence or headquarters of a prefect.
Although the administration of departments and regions is distinct, a regional prefect is ex officio prefect of the department in which the regional prefecture is located. The officeholder has authority upon the other prefects in the region on a range of matters.
^"Préfectures". www.interieur.gouv.fr (in French). Retrieved 2022-01-08.