The Fort de Koenigsmacker (Koenigsmaker, Königsmachern or Kœnigsmacker) is a fortification located to the northeast of Thionville in the Moselle department of France.

The Fort de Koenigsmacker was part of the Moselstellung, a group of eleven fortresses surrounding Thionville and Metz to guard against the possibility of a French attack aimed at regaining Alsace and Lorraine, with construction taking place between 1908 and 1914.

The Fort de Koenigsmacker is located about 4 kilometers (2.5 mi) to the northeast of Thionville on a hilltop overlooking the salient formed by the Cattenom forest and the northern crossings of the Moselle.

Like the Fort d'Illange, Koenigsmacker features an armored battery, originally armed with four short 100 mm guns in single turrets.

Compared to the French Séré de Rivières system forts of the same era, later German fortifications such as Koenigsmacker were scattered over a large area and enclosed chiefly by barbed wire.

[3] Koenigsmacker's fairly compact arrangement includes four dispersed fortified barracks built into a hillside so that their rears are shielded by earth, while the tops and fronts are protected by three or four meters of concrete, and are surmounted by parapets.

The four 100 mm guns in the battery were protected by Schumann turrets and controlled by an armored observation cupola on top of the western barracks.

The whole was surrounded by deep networks of barbed wire, which were swept by fire from small perimeter blockhouses, also linked via the tunnel system.

[4] From 1899, the Germans viewed Metz as a secure position that could provide an anchor for a pivoting movement into France from the Low Countries.

During the Battle of France the Thionville area was bypassed and encircled by German forces, with the Maginot and earlier fortifications seeing little action.

During the Lorraine Campaign of World War II, the U.S. 90th Infantry Division crossed the flooded Moselle early on 9 November 1944.

Fire from Koenigsmacker destroyed bridging equipment and harassed boat-borne troops, but elements of the 358th Infantry Regiment established a lodgement on the east bank and infiltrated the area of the fort before daybreak.