German submarine U-171 was a Type IXC U-boat of Germany's Kriegsmarine built for service during World War II. It was laid down on 1 December 1940 at the DeSchiMAG AG Weser yard at Bremen as yard number 1011, launched on 22 July 1941, and commissioned on 25 October 1941 under the command of Kapitänleutnant Günther Pfeffer.