German submarine U-346 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down at the Nordseewerke in Emden as yard number 218 on 28 October 1942, launched on 13 April 1943 and commissioned on 7 June of the same year under the command of Oberleutnant zur See Arno Leisten. She had been built for operations during the Battle of the Atlantic, but was the victim of an accident before she started operations.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-346 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 AEG GU 460/8-276 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-346 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 20 September 1943, the boat was undergoing diving trials as part of the 8th U-boat flotilla in Danzig Bay in the Baltic Sea; an unknown mechanical fault occurred, sending the submarine into a crash dive from which she never recovered, descending to the bottom of the bay, where she and her crew remain to this day. 37 people died on U-346, but unfortunately for the Kriegsmarine, the personnel aboard the boat were not regular U-boat crew, but a combination of the ship's officers (who were all killed), and dockyard experts on submarine operating systems (six of whom escaped the wreck), whose loss was far more severe than the loss of the boat of its crew, had they been aboard.