German submarine U-1223

German submarine U-1223 was a Type IXC/40 U-boat built for Nazi Germany's Kriegsmarine during World War II.

U-1223 was ordered in 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 6 June 1943. About three months later she was commissioned into service under the command of Kapitänleutnant Harald Bosüner (Crew 35) in the 4th U-boat Flotilla.

While working up for deployment, U-1223 Bosüner was relieved and handed over command to Oberleutnant zur See Albert Kneip (Crew X/39) on 3 March 1944. After completing training, the U-boat transferred to the 2nd U-boat Flotilla and left Kiel for the West Atlantic on 3 August 1944 for her first and only patrol. Stopping briefly in Bergen, Norway, for replenishment, she operated off the Canadian coast, damaging HMCS Magog (K673) on 14 October 1944 and the British steamer SS Fort Thompson on 2 November. Magog was towed back to port, but declared a constructive loss and decommissioned.

U-1223 arrived back in Kristiansand on Christmas Eve, 24 December 1944, and continued her journey to Flensburg, where she arrived three days later. Having been transferred to the 33rd U-boat Flotilla, she left Flensburg again for Königsberg on 5 January 1945, arriving there on the 10th. The U-boat experienced technical problems in the end of January 1945 and had to be towed into Stettin. From there she travelled under tow of GS U-1108 to Wesermünde, where she was decommissioned on 15 April 1945. Most of her crew was ordered to form a tank destroyer unit in Neustadt in Holstein under the command of the 1st watch officer.

When British forces closed in on the port, the U-boat was scuttled in position 53.53333°N, 8.58333°W on 5 May 1945. Her wreck was later broken up for scrap.