German submarine U-857

German submarine U-857 was a Type IXC/40 U-boat of the Nazi German Kriegsmarine built for service during the Second World War. She was ordered on 5 June 1941, laid down on 16 November 1942, and launched on 25 May 1943. For her operational lifespan, she was commanded by Kapitänleutnant Rudolf Premauer and had a crew complement of 59.

She undertook three patrols, the first was for training. She sank two ships for a total tonnage of 15,259 GRT, and damaged one other ship on her last two patrols. She sank the MV Belgian Airman on 14 April 1945, the SS Swiftscout on 18 April 1945 and damaged the MV Katy on 23 April 1945.

U-857 went missing in April 1945 in the North Atlantic Ocean off the east coast of the United States. All hands were lost, and no wreckage was found.

The U-Boat had been claimed to have been sunk by depth charge hedgehogs off the coast of Massachusetts in April 1945 by the USS Gustafson (DE-182) and was also thought to have been possibly sunk by the USS Coffman (DE-191). However more recent commentary surmised that the Gustafson had not hit her, and her loss is currently unexplained. Her wreck currently lies off of Cape Cod.