German submarine U-669 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 3 November 1941 at the Howaldtswerke yard at Hamburg, launched on 5 October 1942, and commissioned on 16 December 1942 under the command of Oberleutnant zur See d.R. Kurt Köhl.
Attached to 5th U-boat Flotilla based at Kiel, U-669 completed her training period on 31 May 1943 and was assigned to front-line service.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-669 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two Siemens-Schuckert GU 343/38–8 double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-669 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, 220 rounds, and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
On the second war patrol U-669 went missing in the Bay of Biscay since 30 August 1943. The U-boat had left St. Nazaire on 29 August and had not been heard of since. Subsequently, U-669 and her crew of 52 was declared missing on 8 September 1943.
U-669 was originally thought to have been sunk on September 7, 1943 in the Bay of Biscay at position 43.36°N -10.13°W by depth charges from a Canadian aircraft. This attack was actually against, inflicting no damage.