The 13.5 cm Kanone 09 (13.5 cm K 09) was a heavy breech-loading field artillery gun used by Germany in World War I. Built by Friedrich Krupp AG, in Essen, Germany, this gun was intended to supplement the 10 cm K 04. Only four were in service at the outbreak of the war. It was withdrawn from service in 1915 as it was deemed to be too much gun for too little shell, but it was returned to service later in the war when the Allied blockade began to affect German ammunition production.