German submarine U-5 was a Type IIA U-boat of the German 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.