Ouvrage Haut-Poirier, Infantry ouvrage of the Maginot Line in Achen, Moselle, France

Ouvrage Haut-Poirier is an underground military fortress in northeastern France consisting of interconnected combat and support structures. The facility features multiple gun positions, barracks spaces, storage areas, and ammunition magazines connected through subterranean passages.

The fortress was constructed between 1934 and 1938 as part of France's defensive strategy during the interwar period. It fell to German forces in 1940 after a brief siege, marking a turning point in the early stages of the Second World War.

The ouvrage is administered by AMEPA, the Association for the Memory and Heritage of Achen, though the town of Achen owns it. Its name comes from the Haut-Poirier height, on cote 340 above the village. The nearby Casemate de Wittring, one of its satellite positions, is kept as a museum and can be visited.

The outer grounds can be explored without restriction, though accessing the underground sections requires prior authorization. Good footwear is advisable since the terrain can be uneven and interior spaces remain damp and cool year-round.

The entry block is reached through a large walkable drain, a reduced entry design shared with the petit ouvrage de Lembach. The ouvrage also has two false cloches, dummy armoured domes meant to draw enemy fire away from the real observation cloches.