The 21 cm Kanone 38 (21 cm K 38) was a heavy gun used by Germany in World War II. Its development began in 1938 after Krupp's success with the 21 cm Mrs 18, but it was not fielded until 1941. It likely equipped Artillerie-Abteilungen 767 and 768, which were the only Heer battalions to field 21 cm guns during the war. Some guns may have served on coastal defence duties as well.