German submarine U-1225 was a Type IXC/40 U-boat of Nazi Germany's Kriegsmarine during World War II.

The submarine was laid down on 28 December 1942 at the Deutsche Werft yard at Hamburg and served as a training unit until transferred into active service 31 May 1944.

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged.

[3] The submarine was laid down on 28 December 1942 at the Deutsche Werft yard at Hamburg, launched on 21 July 1943, and commissioned on 10 November 1943 under the command of Oberleutnant zur See Ernst Sauerberg.

The flying boat was shot down, but not before her depth charges fatally wounded the U-boat.