The 24 cm Kanone 3 (24 cm K 3) was a German heavy siege gun used in the Second World War by the first battalion of Artillerie-Regiment 84. Four were in service when Germany invaded Poland, assigned to the first two batteries of I./AR 84. In the Battle of France the battalion still only had four guns. By Operation Barbarossa all three batteries were equipped with two guns apiece. This situation did not change for the next two years.