|Ordered:||25 September 1939|
|Builder:||Deutsche Werke, Kiel|
|Laid down:||20 November 1939|
|Launched:||28 July 1940|
|Commissioned:||24 July 1940|
|Fate:||Scuttled on 2 May 1945 at Wilhelmshaven|
|Class and type:||IID|
|Height:||8.40 m (27 ft 7 in)|
|Draught:||3.93 m (12 ft 11 in)|
|Test depth:||80 m (260 ft)|
|Complement:||3 officers, 22 men|
German submarine U-139 was a Type IID U-boat of Nazi Germany's Kriegsmarine during World War II. Her keel was laid down on 20 November 1939 by Deutsche Werke in Kiel as yard number 268. She was launched on 28 July 1940 and commissioned on 24 July 1940 with Kapitänleutnant Robert Bartels in command.
U-137 began her service life with the 1st U-boat Flotilla. She was then assigned to the 21st flotilla and subsequently to the 22nd flotilla where she conducted two patrols, but did not sink or damage any ships. She spent the rest of the war as a training vessel.
She was scuttled in May 1945.
German Type IID submarines were enlarged versions of the original Type IIs. U-139 had a displacement of 314 tonnes (309 long tons) when at the surface and 364 tonnes (358 long tons) while submerged. Officially, the standard tonnage was 250 long tons (250 t), however. The U-boat had a total length of 43.97 m (144 ft 3 in), a pressure hull length of 29.80 m (97 ft 9 in), a beam of 4.92 m (16 ft 2 in), a height of 8.40 m (27 ft 7 in), and a draught of 3.93 m (12 ft 11 in). The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of 700 metric horsepower (510 kW; 690 shp) for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of 410 metric horsepower (300 kW; 400 shp) for use while submerged. She had two shafts and two 0.85 m (3 ft) propellers. The boat was capable of operating at depths of up to 80–150 metres (260–490 ft).
The submarine had a maximum surface speed of 12.7 knots (23.5 km/h; 14.6 mph) and a maximum submerged speed of 7.4 knots (13.7 km/h; 8.5 mph). When submerged, the boat could operate for 35–42 nautical miles (65–78 km; 40–48 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 3,800 nautical miles (7,000 km; 4,400 mi) at 8 knots (15 km/h; 9.2 mph). U-139 was fitted with three 53.3 cm (21 in) torpedo tubes at the bow, five torpedoes or up to twelve Type A torpedo mines, and a 2 cm (0.79 in) anti-aircraft gun. The boat had a complement of 25.
The boat's first official patrol commenced with her departure from Windau on 17 July 1941. She arrived in Stormelö without incident on 18 August.
Her second patrol was also abortive, departing Stormelö on 28 August 1941 and arriving in Gotenhafen (Gydnia) on 31 August.
- Helgason, Guðmundur. "The Type IID boat U-139". German U-boats of WWII - uboat.net. Retrieved 12 July 2012.
- Helgason, Guðmundur. "War Patrols by German U-boat U-139". German U-boats of WWII - uboat.net. Retrieved 12 July 2012.
- Gröner 1991, pp. 39–40.
- Busch, Rainer; Röll, Hans-Joachim (1999). German U-boat commanders of World War II : a biographical dictionary. Translated by Brooks, Geoffrey. London, Annapolis, Md: Greenhill Books, Naval Institute Press. ISBN 1-55750-186-6.
- Busch, Rainer; Röll, Hans-Joachim (1999). Deutsche U-Boot-Verluste von September 1939 bis Mai 1945 [German U-boat losses from September 1939 to May 1945]. Der U-Boot-Krieg (in German). IV. Hamburg, Berlin, Bonn: Mittler. ISBN 3-8132-0514-2.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
- Helgason, Guðmundur. "The Type IID boat U-139". German U-boats of WWII - uboat.net. Retrieved 6 December 2014.
- Hofmann, Markus. "U 139". Deutsche U-Boote 1935-1945 - u-boot-archiv.de (in German). Retrieved 30 January 2015.