80 cm K (E)

Schwerer Gustav ( German pronunciation: [ˈʃveːʁɐ ˈɡʊstaf]; lit. 'Heavy Gustav') was a German 80-centimetre (31.5 in) railway gun. Two were developed in the late 1930s by Krupp in Rügenwalde; however, only one was ever actually fired. They were created as siege artillery for the explicit purpose of destroying the main forts of the French Maginot Line, the strongest fortifications in existence at the time. The fully assembled gun weighed nearly 1,350 tonnes (1,490 short tons) and could fire high-explosive shells weighing 4.8 t (5.3 short tons) to a range of 47 km (29 mi), or armour-piercing shells weighing 7.1 t (7.8 short tons) to a range of 38 km (24 mi).

The guns were designed in preparation for the Battle of France but were not ready for action when that battle began, and the Wehrmacht offensive through Belgium rapidly outflanked and isolated the Maginot Line, which was then besieged with more conventional heavy guns until French capitulation. Gustav was later deployed in the Soviet Union during the Battle of Sevastopol, part of Operation Barbarossa, where, among other things, it destroyed a munitions depot located roughly 30 m (98 ft) below sea level. The gun was moved to Leningrad, and may have been intended to be used in the Warsaw Uprising like other German heavy siege pieces, but the uprising was crushed before it could be prepared to fire. Gustav was destroyed by the Germans near the end of the war in 1945 to avoid capture by the Soviet Red Army.