German submarine U-673 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 20 January 1942 at the Howaldtswerke yard at Hamburg, launched on 27 February 1943, and commissioned on 8 May 1943 under the command of Oberleutnant zur See Gerhard Haelbich.
Attached to 5th U-boat Flotilla based at Kiel, U-673 completed her training period on 31 May 1944 and was assigned to front-line service.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-673 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-673 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), one 3.7cm (01.5inches) Flak M42 and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
On 14 September 1944, U-673 left St. Nazaire, France, for Norway, reaching Bergen on 19 October 1944. There the U-boat joined a convoy south. Early on 24 October 1944, U-673 collided with north of Stavanger and was beached at Smaaskjaer. Later the U-boat was salvaged and towed to Stavanger. U-673 remained in Stavanger for the rest of the war and became British war booty in 1945. In 1946 the U-boat was broken up for scrap.