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