Korvettenkapitän Siegfried Freiherr von Forstner (19 September 1910 – 13 October 1943) was a German U-boat commander during World War II. He was also a recipient of the Knight's Cross of the Iron Cross (). The Knight's Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership. He and his entire crew of were killed in action on 13 October 1943.