German submarine U-125 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.

[1] U-125 departed Kiel on 15 July 1941 on her first patrol, under the command of Kapitänleutnant Günter Kuhnke, arriving in the recently captured French Atlantic port of Lorient fourteen days later.

[3] U-125 had her first success on her third patrol, under her new commander Kapitänleutnant Ulrich Folkers, sinking the American merchant ship West Ivis off Cape Hatteras, North Carolina on 26 January 1942.

She made her first attack on the 23rd, sinking the American merchant ship Lammot Du Pont, about 500 nmi (930 km; 580 mi) south-east of Bermuda.

Following the demise of Camayagua, a US Navy aircraft unsuccessfully searched for the U-boat; then flew to Georgetown where it dropped a note in the Commissioner's garden with information on the survivors.

[6] U-125's next patrol, the fifth, beginning on 27 July 1942, took her to the coast of West Africa, where she sank six merchant ships between 1 September and 8 October, returning to Lorient on 6 November 1942.

Following the sinking of Baron Ogilvy on 29 September, the survivors sighted a small convoy on 1 October and succeeded in attracting their attention with flares.

[7] U-125 sailed on her sixth patrol on 9 December 1942, out into the central Atlantic, south-west of the Azores, but she made no attacks before returning to Lorient on 19 February 1943.

Nevertheless, the boat only sank one ship, on 4 May south of Cape Farewell (Greenland), she was perhaps ironically called Lorient, a straggler from ONS-5; there were no survivors.