German submarine U-666 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II.She was laid down on 16 September 1941 by Deutsche Werft, Hamburg as yard number 815, launched on 18 July 1942 and commissioned on 26 August 1942 under Kapitänleutnant Herbert Engel. Oberleutnant zur See Ernst Wilberg took over command on 10 December 1943.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-666 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-666 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 26 August 1942, followed by active service on 1 March 1943 as part of the 6th Flotilla for the remainder of her service.
In four patrols she damaged 1 merchant ship, for a total of and sank one warship (1,370 tons).
On 19 March 1943, after damaging the Greek freighter Carras, a B-17 Flying Fortress bomber from No. 220 Squadron RAF hit the boat with four depth charges, causing sufficient damage as to force her to return to France.
U-666 took part in 14 wolfpacks, namely:
U-666 was sunk on 10 February 1944 in the North Atlantic west of Ireland, in position 53.56N, 17.16W, by depth charges from a Swordfish aircraft (842 Sqn FAA/A) of the British escort carrier HMS Fencer. 51 dead (all hands lost).
| Date | Ship Name | Nationality | Tonnage[1] | Fate[2] | |
|---|---|---|---|---|---|
| 19 March 1943 | Carras |  Greece | 5,234 | Damaged | |
| 23 September 1943 | 1,370 | Sunk |