German submarine U-857 was a Type IXC/40 U-boat of Nazi Germany's 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.