German submarine U-1305 was a Type VIIC/41 U-boat of Nazi Germany's Kriegsmarine during World War II.
She was ordered on 1 August 1942, and was laid down on 30 July 1943, at Flensburger Schiffbau-Gesellschaft, Flensburg, as yard number 498. She was launched on 11 July 1944, and commissioned under the command of Oberleutnant zur See Helmuth Christiansen on 13 September 1944.
German Type VIIC/41 submarines were preceded by the heavier Type VIIC submarines. U-1305 had a displacement of when at the surface and while submerged. She had a total length of , a pressure hull length of , an overall beam of , a height of , and a draught of . The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of for use while surfaced, two AEG GU 460/8-276 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-1305 was fitted with five torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one SK C/35 naval gun, (220 rounds), one Flak M42 and two C/30 anti-aircraft guns. The boat had a complement of between forty-four and fifty-two.
On 10 May 1945, U-1305 surrendered at Loch Eriboll, Scotland. She was later transferred to Lisahally on 14 May 1945.
The TNC allocated U-1305 to the Soviet Union. On 4 December 1945, she arrived in Libau, Latvia, as British N-class N25. On 13 February 1946, the Soviet Navy allocated her to the Baltic Fleet. She was renamed S-84 on 9 June 1949, then sent to the reserve fleet on 30 December 1955. S-84 went to the Northern Fleet as a test hulk and was later sunk in the Barents Sea on 10 October 1957, during an atomic bomb test off of Novaya Zemlya.
The wreck now lies approximately at .