The 28 cm SK L/40 was a German naval gun that was used in World War I and World War II by two classes of German pre-dreadnought battleships. It was the first large German naval gun to use a horizontal sliding block breech design rather than the interrupted screw more commonly used in guns of this size; it was also the last large German naval gun to load all its propellant in a single case. It was adapted for land service after the pre-dreadnoughts began to be disarmed beginning in 1916. Four guns served on coast defense duties on the island of Wangerooge during World War I on fixed mounts. During World War II these guns were transferred to Brest. Others were used in railway mountings in both World Wars.