German submarine U-3515 was a Type XXI U-boat (one of the "Elektroboote") of Nazi Germany's Kriegsmarine, built for service in World War II.

She was ordered on 6 November 1943, and was laid down on 27 August 1944 at F Schichau GmbH, Danzig, as yard number 1660.

She was launched on 4 November 1944, and commissioned under the command of Oberleutnant zur See Fedor Kuscher on 14 December 1944.

[3] The submarine was powered by two MAN SE supercharged six-cylinder M6V40/46KBB diesel engines each providing 4,000 metric horsepower (2,900 kilowatts; 3,900 shaft horsepower), two Siemens-Schuckert GU365/30 double-acting electric motors each providing 5,000 PS (3,700 kW; 4,900 shp), and two Siemens-Schuckert silent running GV232/28 electric motors each providing 226 PS (166 kW; 223 shp).

Redesignated as test hulk B-100 on 2 July 1958, until finally being struck from the Soviet Navy on 25 September 1959, and broken up for scrap on 30 November 1959.