German submarine U-671 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 2 December 1941 at the Howaldtswerke yard at Hamburg, launched on 15 December 1942, and commissioned on 3 March 1943 under the command of Oberleutnant zur See August-Wilhelm hewicker.
Attached to 5th U-boat Flotilla based at Kiel, U-671 completed her training period on 30 April 1944 and was assigned to front-line service.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-671 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-671 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 and last war patrol, U-671 was detected by two British warships in the English Channel south of Brighton in the early hours of 4 August 1944. attacked with depth charges and hedgehogs causing severe damage to the U-boat. Stayner was later joined by . Repeated attacks resulted in an oil spill and a number of survivors appeared at the surface. Of the crew of 52 all but five perished in the attack.