Royal Saxon Jagdstaffel 21 was a "hunting group" (i.e., fighter squadron) of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I. As one of the original German fighter squadrons, the unit would score 148 verified aerial victories, including at least 30 destructions of enemy observation balloons. In turn, their casualties for the war would amount to eight pilots killed in action, six wounded in action, and one fallen prisoner of war.