German submarine U-1221 was a Type IXC/40 U-boat built for Nazi Germany's Kriegsmarine during World War II.
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-1221 had a displacement of 1144t when at the surface and 1257t while submerged. The U-boat had a total length of 76.76m (251.84feet), a pressure hull length of 58.75m (192.75feet), a beam of 6.86m (22.51feet), a height of 9.6m (31.5feet), and a draught of 4.67m (15.32feet). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4400PS for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1000shp for use while submerged. She had two shafts and two 1.92abbr=onNaNabbr=on 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-1221 was fitted with six 53.30NaN0 torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.52NaN2 SK C/32 naval gun, 180 rounds, and a 3.7sp=usNaNsp=us SK C/30 as well as a 2sp=usNaNsp=us C/30 anti-aircraft gun. The boat had a complement of forty-eight.
U-1221 was ordered on 25 August 1941 from Deutsche Werft, AG in Hamburg under the yard number 384. Her keel was laid down on 28 October 1942 and the U-boat was launched the following year on 26 May 1943. She was commissioned into service under the command of Oberleutnant zur See Karl Kölzer (Crew 31) in the 4th U-boat Flotilla on 11 August 1943.
On 20 January 1944, Kölzer handed over command to Oberleutnant zur See Paul Ackermann (Crew XII/39), who took her on her first—and only—patrol in the West Atlantic from 20 August until 28 November 1944.
During an air raid by Eighth Air Force on Kiel, U-1221 was hit by two bombs in the fore-ship on 3 April 1945. The U-boat sank immediately, taking the skeleton crew of 18 with her. Seven of her crew perished, while the rest was rescued through the stern torpedo tubes the next day.