German submarine U-243 was a Type VIIC U-boat of the Nazi German Kriegsmarine during World War II. An order was placed for U-243 on 10 April 1941 and construction began on 28 October 1942 at Germaniawerft, Kiel, as 'werk' 677. She was launched the following year on 2 September 1943 and commissioned on 2 October under the command of Oberleutnant Hans Märtens. Three days into her only patrol, she shot a German aircraft down. She was sunk in the Bay of Biscay in July 1944