German submarine U-3520 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 20 September 1944 at F Schichau GmbH, Danzig, as yard number 1665. She was launched on 23 November 1944, and commissioned under the command of Kapitänleutnant Sarto Ballert on 12 January 1945.
