Districts are administrative divisions of the State. They are geographic areas that have the sub-prefecture as their administrative centre. The sub-prefect is responsible for its administration; he acts as a relay of the prefect by performing the administrative supervision of the municipalities in his district. The name of the district is usually that of the administrative centre. All administrative centre municipalities belong to a district that bears their name with the exception of the districts of Metz-Campagne (57-4), Thionville-Ouest (57-8) and Strasbourg-Campagne (67-6). The district is a subdivision of the department and a group of cantons that respects the boundaries of municipalities.
Districts as subdivisions of Departments should not be confused with the municipal districts, which are subdivisions of the three largest French cities.