German submarine U-257 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down at the Bremer Vulkan yard at Bremen-Vegesack on 22 February 1941 as yard number 22. She was launched on 19 November and commissioned on 14 January 1942 under the command of Kapitänleutnant Heinz Rahe.
U-257 was assigned to the 5th U-Boat Flotilla for training, then transferred to the 3rd U-boat Flotilla for operational service.
She was sunk by Allied warships in mid-Atlantic on 24 February 1944.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-257 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 460/8–27 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-257 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 carried out six patrols, but did not sink or damage any ships. She was a member of seven wolfpacks.
U-257s first patrol began on 21 September 1942 from Bergen in Norway. Her route took her across the North Sea, through the gap between the Faroe and Shetland Islands and into the Atlantic Ocean. She docked at La Pallice in occupied France, on 18 October.
These sorties passed without major incident.
The boat was attacked from the air twice in one day. U-257, in the company of and was transitting the Bay of Biscay, outbound on 14 June 1943, when a Sunderland flying boat of 228 Squadron RAF unsuccessfully depth charged the three boats. In the afternoon, it was much the same story, but this time a Whitley from No. 10 OTU was involved. One man from the U-boat's crew was wounded. A second Whitley from the same unit arrived, but could only exchange fire with the submarine as it had expended all its depth charges in a previous engagement, the boat escaped.
The submarine had moved to St. Nazaire; she departed from this French Atlantic port on 2 January 1944. On 24 February, she was attacked and sunk in mid-Atlantic by the Canadian frigate, assisted by . (A former crew member from Waskesiu has stated that Nene merely picked survivors up). Thirty men died in the sinking, there were nineteen survivors.
U-257 took part in seven wolfpacks, namely: