German submarine U-1222 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-1222 had a displacement of when at the surface and while submerged. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of for use while surfaced, two Siemens-Schuckert 2 GU 345/34 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-1222 was fitted with six torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one SK C/32 naval gun, 180 rounds, and a Flak M42 as well as two twin C/30 anti-aircraft guns. The boat had a complement of forty-eight.
U-1222 was ordered on 25 August 1941 from Deutsche Werft in Hamburg-Finkenwerder under the yard number 385. Her keel was laid down on 2 November 1942 and was launched the following year on 9 June 1943. About three months later she was commissioned into service on 1 September 1943 under the command of Kapitänleutnant Heinz Bielfeld (Crew 34) in the 4th U-boat Flotilla.
After work-up for deployment, U-1222 transferred to the 10th U-boat Flotilla and left Kiel for the West Atlantic on 13 April 1944 for her first and only patrol. Stopping briefly in Marvik, Norway, for replenishment, she operated with no success south of Nova Scotia.
Returning from patrol, U-1222 was charging her batteries while submerged, when her snorkel was spotted by a British aircraft, Sunderland 'P' of No. 201 Squadron RAF, on 11 July 1944 off La Rochelle. The aircraft immediately attacked the U-boat with depth charges and sank her. All 56 crew members died in the event.