A railway gun, also called a railroad gun, is a large artillery piece, often surplus naval artillery, mounted on, transported by, and fired from a specially designed railway wagon. Many countries have built railway guns, but the best-known are the large Krupp-built pieces used by Germany in World War I and World War II. Smaller guns were often part of an armoured train. Only able to be moved where there were good tracks, which could be destroyed by artillery bombardment or airstrike, railway guns were phased out after World War II.

Krupp, also known as Friedrich Krupp AG and later Friedrich Krupp AG Hoesch-Krupp after acquiring Hoesch AG in 1991, was the largest company in Europe at the beginning of the 20th century as well as Germany's premier weapons manufacturer during both world wars. From the Thirty Years' War to the end of World War II, it produced battleships, U-boats, tanks, howitzers, guns, utilities, and hundreds of other commodities. The company also produced steel used to build railroads in the United States and to cap the Chrysler Building.