German submarine U-665 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II.She was laid down on 10 June 1941 by Deutsche Werft, Hamburg as yard number 814, launched on 9 June 1942 and commissioned on 22 July 1942 under Leutnant zur See Hans-Jürgen Haupt.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-665 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-665 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.
The boat's career began with training at 5th U-boat Flotilla on 22 July 1942, followed by active service on 1 February 1943 as part of the 1st Flotilla for the remainder of her short service. In her sole patrol she sank one merchant ship, for a total of .
U-665 took part in three wolfpacks, namely:
U-665 has been missing since 22 March 1943 in the Bay of Biscay, west of La Pallice.
U-665 was thought to have been sunk on 22 March 1943 in the Bay of Biscay west of Nantes at 46.7833°N -67°W, by depth charges from Vickers Wellington aircraft of No. 172 Squadron RAF (call-sign G). This attack was actually against U-448, inflicting no damage.
U-665 was also thought to have been sunk on 22 March 1943 in the North Atlantic at 48.0667°N -36°W, by depth charges from an Armstrong Whitworth Whitley VII of No. 10 Operational Training Unit RAF (10 OTU) (call-sign Q), for the loss of all hands.