German submarine U-559 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II.

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 Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged.

For her third patrol, beginning on 20 September, she was assigned to the 'Goeben' group, which were the first U-boats to enter the Mediterranean in World War II through the heavily defended Strait of Gibraltar.

On her fourth patrol, she torpedoed and sank the Australian sloop HMAS Parramatta off the Libyan coast; although most survivors were picked up by other ships, three men managed to reach dry land where they were rescued by advancing British troops.

Having moved to Pula in Croatia in March 1942, she then sortied on 18 May, and sank the tanker Athene and damaged the oiler Brambleleaf in a convoy attack on 10 June.

After dark, U-559, with a cracked pressure hull, unable to maintain level trim and four of her crew dead from explosions and flooding, was forced to the surface.

[1][9] The German crew hurriedly scrambled overboard without destroying their codebooks or Enigma machine and, crucially, having failed to open all the sea-water vents to scuttle the U-boat properly.

Three Royal Navy sailors, Lieutenant Anthony Fasson, Able Seaman Colin Grazier and NAAFI canteen assistant Tommy Brown, then boarded the abandoned submarine.

Two German crew members, rescued from the sea, watched this material being loaded into Petard's whaler but were dissuaded from interfering by an armed guard.

He was discharged and returned home to North Shields, only to die two years later attempting to rescue his younger sister from a house fire.

[13] The code-book material they retrieved was immensely valuable to the code-breakers at Bletchley Park, who had been unable to read the 4-rotor U-boat Enigma for ten months since its introduction by the German Kriegsmarine at the beginning of 1942.