The 21 cm L/35 were a family of German naval artillery developed in the years before World War I and used in limited numbers. This gun armed warships of the Argentine Navy, Imperial Chinese Navy, Royal Danish Navy, Imperial Japanese Navy and Royal Netherlands Navy before and after World War I. It was used in the First Sino-Japanese War, Boxer Rebellion and a ship captured by Japan in the Sino-Japanese War was later used in the Russo-Japanese War.