Moselle is the most populous department in Lorraine, in the northeast of France, and is named after the river Moselle, a tributary of the Rhine, which flows through the western part of the department. It had a population of 1,046,543 in 2019. Inhabitants of the department are known as Mosellans.

In the administrative divisions of France, the department is one of the three levels of government under the national level, between the administrative regions and the communes. Ninety-six departments are in metropolitan France, with an additional five constituting overseas departments, which are also classified as overseas regions. Departments are further subdivided into 333 arrondissements and 2,054 cantons. These last two levels of government have no political autonomy, instead serving as the administrative basis for the local organisation of police, fire departments as well as, in certain cases, elections.