German submarine U-1303 was a Type VIIC/41 U-boat of Nazi Germany's Kriegsmarine during World War II.
She was ordered on 2 April 1942, and was laid down on 8 April 1943, at Flensburger Schiffbau-Gesellschaft, Flensburg, as yard number 496. She was launched on 10 February 1944, and commissioned under the command of Oberleutnant zur See Heinz Baum on 5 April 1944.
German Type VIIC/41 submarines were preceded by the heavier Type VIIC submarines. U-1303 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-1303 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.
U-1303 was scuttled in Kupfermühle Bay near Flensburg on 5 May 1945 as part of Operation Regenbogen. Her wreck was raised and broken up later.