France is divided into 18 administrative regions of which 13 are located in metropolitan France, i.e. on the European continent, while the other five are overseas regions, not be confused with the "overseas collectivities", which have a semi-autonomous status.
All 13 mainland administrative regions (including Corsica as of 2019) are further subdivided into 2 to 13 administrative departments, with the prefect of each region's administrative centre's department also acting as the regional prefect.
The overseas regions administratively consist of only one department each and hence also have the status of "overseas departments".
Most administrative regions also have the status of regional "territorial collectivities", which comes with a local government, with departmental and communal collectivities below the region level.
The exceptions are Corsica, the French Guiana, Mayotte, and Martinique, where region and department functions are managed by single local governments having consolidated jurisdiction, and which are known as "single territorial collectivities".