German submarine U-63 was a Type IIC U-boat of Nazi Germany's Kriegsmarine that served in the Second World War. She was built by Deutsche Werke AG, Kiel. Ordered on 21 July 1937, she was laid down on 2 January 1939 as yard number 262. She was launched on 6 December 1939 and commissioned on 18 January 1940 under the command of Oberleutnant zur See Günther Lorentz.
U-63 was initially assigned to the 1st U-boat Flotilla during her training period, until 1 February 1940. She stayed with that organization until her sinking.
German Type IIC submarines were enlarged versions of the original Type IIs. U-63 had a displacement of when at the surface and while submerged. Officially, the standard tonnage was , however. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of for use while submerged. She had two shafts and two 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-63 was fitted with three torpedo tubes at the bow, five torpedoes or up to twelve Type A torpedo mines, and a anti-aircraft gun. The boat had a complement of 25.
U-63 left the German island of Helgoland (also known as 'Heligoland'), on 17 February 1940. She, along with five other U-boats, took part in Operation Nordmark, a reconnaissance mission for the German Battleships and and Cruiser Admiral Hipper (for what proved to be an unsuccessful sortie). It took place in the vicinity of the Orkney and Shetland Islands between 18 and 20 February.
The boat sank the Santos off Kirkwall, Orkney, on 24 February 1940.
U-63 was sunk on 25 February 1940 by a mix of depth charges and torpedoes from the British warships , and and the submarine south of Shetland. The approximate location of the wreck site is .
One man died, there were 24 survivors. Those who survived spent the remainder of the war as POWs.