German submarine U-129 was a Type IXC U-boat of the Nazi German Kriegsmarine during World War II. She was laid down at the AG Weser yard, Bremen as 'werk' 992 on 30 July 1940, launched on 28 February 1941 and was commissioned on 21 May with Kapitänleutnant Nicolai Clausen in command. Her service life began with training in the 4th U-boat Flotilla; she moved to the 2nd Flotilla for operations on 1 July 1941. She sank 29 ships, a total of 143,748 tons, on ten patrols.