Fort de Plappeville, Military fortification in Plappeville, France.

Fort de Plappeville is a military fortification situated on high ground near Metz, featuring thick defensive walls, gun emplacements, and a bastion design. The structure was created to command the Moselle valley and protect French border territory.

Work on the fort began in 1867 under Napoleon III and was completed by German forces following the 1870 war. Its design reflected French defensive strategies of the late 1800s.

The fort was renamed Feste Alvensleben in 1872 after Prussian general Constantin von Alvensleben, who commanded the III Army Corps in the 1870–71 war. From 1897 two armoured batteries, each with four rotating turrets for 150 mm guns, stood on the Lessy pass side. The site is now closed for pyrotechnic clearance while Metz-Métropole runs a long restoration of its built and natural heritage.

Access to the fort is currently forbidden: the former military site is closed while pyrotechnic clearance is carried out. Metz-Métropole has begun a long-term restoration of the architectural and natural heritage. The site can only be viewed from the outside, from the surrounding plateau paths.

During World War I, the fort served as a rest stop for German soldiers heading to the Battle of Verdun. Later in World War II, it functioned as a disciplinary facility.