German submarine U-129 was a Type IXC U-boat of Nazi Germany's Kriegsmarine during World War II.

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 metric horsepower (740 kW; 990 shp) for use while submerged.

The boat's first patrol involved her departure from Horten, crossing the North Sea and entering the Atlantic Ocean by passing close to the Faroe Islands on the Icelandic side.

Things improved dramatically when as part of Operation Drumbeat,[2] it attacked Nordvangen on 20 February; this ship sank in one minute northeast of Trinidad.

1926 D/S Cadmus (UKJ101192601) Torpedoed and sunk 01/07 by the German submarine U 129 (Kapitänleutnant Hans Ludwig Witt) in position 22.50N-92.30W while on a voyage from Tela, Honduras to Galveston, TX, USA with bananas.

1927 MS GUNDERSEN (UKJ101192702) Departed Tela, Honduras 29/06 with 16.255 banana stems for Galveston, TX, USA.

The submarine returned to its sunshine haunts; included in the toll was Hardwicke Grange, which was sunk with torpedoes and the deck gun north of Puerto Rico on 12 June 1942.

It also sank Millinocket on 17 June off La Isabela, Cuba and a ship from the Soviet Union, Tuapse, in the Gulf of Mexico on 4 July.