Ajoncourt is a commune in the Moselle department in the Grand Est region of north-eastern France. Located in the historical and cultural region of Lorraine, it is situated approximately 25 kilometers southeast of Metz and 30 kilometers northeast of Nancy.
As an administrative division, Ajoncourt is part of the arrondissement of Sarrebourg-Château-Salins and the canton of Saulnois. Its official INSEE code is 57007, and its postal code is 57590. The commune is typically characterized by a small, rural population.