German submarine U-1226 was a Type IXC/40 U-boat of Nazi Germany's Kriegsmarine during World War II. The U-boat, built for service in the Battle of the Atlantic, was completed in Hamburg in November 1943, and placed under the command of Oberleutnant zur See August-Wilhem Claussen (Crew X/37), whose brother Emil had been killed on board U-469 the previous year. She underwent working up cruises in the Baltic Sea before embarking on her only operational patrol from Horten Naval Base in Norway during September 1944.