German submarine U-155 was a Type IXC U-boat of Nazi Germany's Kriegsmarine built for service during World War II. Her keel was laid down on 1 October 1940 by DeSchiMAG AG Weser in Bremen as yard number 997. She was launched on 12 May 1941 and commissioned on 23 August with Kapitänleutnant Adolf Piening in command. Piening was relieved in February 1944, by Oberleutnant zur See Johannes Rudolph.

The Type IX U-boat was designed by Nazi Germany's Kriegsmarine in 1935 and 1936 as a large ocean-going submarine for sustained operations far from the home support facilities. Type IX boats were briefly used for patrols off the eastern United States in an attempt to disrupt the stream of troops and supplies bound for Europe. It was derived from the Type IA, and appeared in various sub-types.