German submarine U-2331 was a Type XXIII U-boat built for Nazi Germany's Kriegsmarine during World War II and intended for service against allied shipping in coastal waters. She was a brand new, high-technology electric U-boat which was lost when only one month old in a bizarre training accident in the Baltic Sea. Built at Hamburg, she was constructed at speed, as she and her sisters were seen as war winning weapons and thus vitally important to the German war effort.