German submarine U-1221 was a Type IXC/40 U-boat built for Nazi Germany's Kriegsmarine during World War II.

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged.

[1] U-1221 was ordered on 25 August 1941 from Deutsche Werft, AG in Hamburg under the yard number 384.

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.