The 17 cm SK L/40 was a Kaiserliche Marine naval gun that was used on two classes of German pre-dreadnought battleships the Braunschweig-class and the Deutschland-class as their secondary battery. Later they were adapted for land service during World War I and World War II.

The Braunschweig-class battleships were a group of five pre-dreadnought battleships of the German Kaiserliche Marine built in the early 1900s. They were the first class of battleships authorized under the Second Naval Law, a major naval expansion program. The class comprised five ships—Braunschweig, Elsass, Hessen, Preussen, and Lothringen—and they were an improvement over the preceding Wittelsbach class. The Braunschweigs mounted a more powerful armament of 28 cm (11 in) and 17 cm (6.7 in) guns. Less than two years after the first members of the class entered service, the ships were rendered obsolescent by the British all-big-gun battleship Dreadnought, which curtailed their careers.