German submarine U-1234 was a Type IXC/40 U-boat of Nazi Germany's Kriegsmarine built during World War II for service in the Battle of the Atlantic.

She was given to Kapitänleutnant Helmut Thurmann to command, and he began her process of mechanical testing and operational training in the Baltic Sea.

The boat was holed and rapidly began to sink, slipping below the waves leaving her commander and most of her crew bobbing in the sea.

Such severe damage had been done to her vital systems however that she was no longer suitable for full combat duty, and was seconded to a training flotilla, where she remained to the end of the war.

On 5 May 1945 her crew took her into the Hörup Haff off Flensburg and scuttled her to keep her from falling into Allied hands as their ground forces approached the port.