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 (German: Ritterkreuz des Eisernen Kreuzes). 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 U-402 were killed in action on 13 October 1943.