Ouvrage Bréhain is part of the Fortified Sector of the Crusnes of the Maginot Line, located near the community of Bréhain-la-Ville in the Meurthe-et-Moselle department of France. Bréhain is flanked by petits ouvrages Mauvais Bois and Aumetz. The gros ouvrage was equipped with long-range artillery, and faced the border with Luxembourg. It saw no major action in either the Battle of France in 1940 or the Lorraine Campaign of 1944. While not open to public visitation, it has been secured and is in relatively good condition when compared to other abandoned Maginot positions. A flanking casemate has been restored and may be visited.

The Fortified Sector of the Crusnes was the French military organization that in 1940 controlled the section of the Maginot Line extending eastwards approximately 28 kilometres (17 mi) from Longuyon. The sector roughly follows the valley of the Crusnes river. Crucially, the trace of the Maginot Line in the Crusnes sector is about 7 kilometres (4.3 mi) behind the industrial city of Longwy which sits directly against the French borders with Belgium and Luxembourg. The Crusnes sector was one of the strongest Maginot Line sectors. It was attacked in 1940 by German forces in the Battle of France. Despite the withdrawal of the mobile forces that supported the fixed fortifications, the sector successfully fended off German assaults before the Second Armistice at Compiègne. The positions and their garrisons finally surrendered on 27 June 1940. Following the war many positions were reactivated for use during the Cold War. Three locations are now preserved and open to the public, with a fourth position under restoration.