The V-3 (German: Vergeltungswaffe 3, was a German World War II large-caliber gun working on the multi-charge principle whereby secondary propellant charges are fired to add velocity to a projectile, built in tunnels and permanently aimed at London, England.

V-weapons, known in original German as Vergeltungswaffen, were a particular set of long-range artillery weapons designed for strategic bombing during World War II, particularly strategic bombing and/or aerial bombing of cities. They were the V-1, a pulsejet-powered cruise missile; the V-2, a liquid-fueled ballistic missile ; and the V-3 cannon. Germany intended to use all of these weapons in a military campaign against Britain, though only the V-1 and V-2 were so used in a campaign conducted 1944–45. After the invasion of western Europe by the Allies, these weapons were also employed against targets on the mainland of Europe, mainly in France and Belgium. Strategic bombing with V-weapons killed approximately 18,000 people, mostly civilians. The cities of London, Antwerp and Liège were the main targets.