German submarine U-5 was a Type IIA U-boat of Nazi Germany's Kriegsmarine. She was laid down on 11 February 1935, launched on 14 August and commissioned 31 August that year, under Oberleutnant zur See Rolf Dau.
U-5 served mostly as a training boat from 1935 to 1940, but did see two wartime patrols in 1940. She was transferred to the 21st U-boat Flotilla on 1 July 1940.
U-5 was sunk on 19 March 1943 in a diving accident west of Pillau (now Baltiysk in Russia); 16 of the 37-man crew survived.
German Type II submarines were based on the . U-5 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-5 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.