German submarine U-255 was a Type VIIC U-boat that served in Nazi Germany's Kriegsmarine during World War II.

The submarine was laid down on 21 December 1940 at the Bremer Vulkan yard at Bremen-Vegesack, launched on 8 October 1941 and commissioned on 29 November 1941 under the command of Kapitänleutnant Reinhart Reche.

The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two AEG GU 460/8–27 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged.

[6] She made her first kill on 6 July, sinking the 7,191 GRT American Liberty ship John Witherspoon about 20 miles (32 km) off Novaya Zemlya.

The ship, en route from Baltimore to Arkhangelsk with 8,575 tons of ammunition and tanks aboard, had been a part of Convoy PQ 17 which had dispersed on Admiralty orders in the Barents Sea on 4 July.

[7] The next day, 7 July, she sank the 5,116 GRT American Hog Islander Alcoa Ranger, also from Convoy PQ 17.

[9] On 13 July U-255 found the 7,168 GRT Dutch merchant ship Paulus Potter abandoned and drifting, with 2,250 tons of general goods, ammunition, 34 tanks, 15 aircraft and 103 trucks aboard.

The ship had been attacked by Ju 88 dive bombers of III./KG 30 east-north-east of Bear Island on 5 July, the day after Convoy PQ 17 dispersed.

All 76 of the crew had taken five days to reach land at Novaya Zemlya, eventually being rescued by a Soviet whaling vessel.

[12] There, on 20 September, she attacked the 4,937 GRT American merchant ship Silver Sword, returning from Arkhangelsk to New York City with 5,000 tons of hides and chrome ore and a deck cargo of wood pulp.

Hit by two torpedoes, which blew off the stern post, propeller and rudder, and caused the after magazine to explode, the 48 crew and 16 passengers (survivors from PQ 17) abandoned ship in two lifeboats and one raft.

[2] There the submarine was fitted with a Schnorchel underwater-breathing apparatus[1] before sailing again on 7 January 1943, and arriving at Hammerfest in northern Norway on the 18th.

[2] Returning to her old hunting grounds north of Norway, U-255 sailed from Hammerfest on 23 January 1943,[14] and on the 26th, U-255 likely sank the 2,418 GRT Soviet merchant ship Krasnyj Partizan with two torpedoes west of Bear Island.

[15][16] On the afternoon of 3 February, about 600 miles (970 km) northeast of Iceland, U-255 fired a salvo of torpedoes at Convoy RA 52, en route from Murmansk to New York, and hit the 7,460 GRT American merchant ship Greylock.

[18] On 5 March she fired a spread of three torpedoes at Convoy RA 53, sailing from Murmansk to Scotland, and hit two American merchant ships; the 4,978 GRT Hog Islander Executive, loaded with 1,500 tons of potassium chloride, and the 7,191 GRT Liberty ship Richard Bland, carrying 4,000 tons of lumber.

Executive was struck on the starboard side; the explosion demolished the booms, engine, dynamos and all equipment in the immediate area.

The ship remained with the convoy, but on the night of 6 March lost contact in gale-force winds and rough seas, and proceeded alone towards Iceland.

Five days later, on 10 March, U-255 found the vessel about 35 miles (56 km) off Langanes, Iceland, and hit her with two more torpedoes, breaking the ship in two just forward of the bridge.

The crew abandoned ship, and of the total of 69 on board, the master, five officers, 13 crewmen and 15 armed guards were lost, when their lifeboats were swamped in heavy seas.

[1] Under the command of Oberleutnant zur See Erich Harms (the U-boat's former I.WO) from 7 June 1943,[1] U-255 sailed from Bergen on 9 July, arriving at Narvik on the 16th.

[23] U-255 established a secret seaplane base on Novaya Zemlya,[3] and returned to Narvik on 19 September after 63 days at sea.

[24] On 10 March, about 400 miles (640 km) south of Iceland, U-255 located Convoy CU 16, but was detected by sonar by the US Navy destroyer escort Leopold.