Ouvrage Chesnois, Military fortification in Montmédy region, France

Ouvrage Chesnois is a military fortification in the Montmédy region and consists of six combat blocks connected by underground passages. The installation was equipped with various weapon systems and was designed to protect an area against attacks from outside.

The installation was built in the 1930s as part of French border defense against Germany. It saw brief action during the 1940 campaign before being abandoned.

The name Chesnois comes from the local place-name, also written Chênois. The mixed entry is one of only two true mixed entries in the northeast of the Maginot Line, the other being Vélosnes. Above the entry, modified GFM cloches were fitted to vent exhaust gases from the four SMIM 90-horsepower generators of the underground power plant.

The interior is sealed and cannot be entered; bats use the underground galleries, which were fitted out for their protection. Surface elements, including the blocks and the mixed entry, remain visible and can be approached on foot. The site is abandoned and reported to be dangerous to enter.

The mixed entry is topped, set back from the defensive GFM cloches, by modified GFM cloches used to vent exhaust gases from the power plant's engines. The underground galleries run more than 2,000 metres from end to end, and a 365-metre drain from Block 7 serves as an emergency exit.