German submarine U-110 was a Type IXB U-boat of Nazi Germany's Kriegsmarine that operated during World War II.

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 metric horsepower (740 kW; 990 shp) for use while submerged.

This ship only escaped after she was hit by a torpedo which failed to detonate, (although it left a large dent) and the U-boat's 105 mm deck gun crew forgot to remove the tampion in the muzzle before engaging their target.

U-110 arrived in Lorient on the French Atlantic coast on 29 March, having cut the patrol short due to damage from the exploding gun.

On the 27th, she sank Henri Mory about 330 nautical miles (610 km; 380 mi) west northwest of Blasket Islands, Ireland.

Broadway shaped course to ram, but fired two depth charges beneath the U-boat instead, in an endeavour to make the crew abandon ship before scuttling her.

The British had believed that the German deck gun was to be used and ceased fire when they realised that the U-boat was being abandoned and the crew wanted to surrender.

Bulldog's boarding party, led by Sub-Lieutenant David Balme, got onto U-110 and stripped it of everything portable, including her Kurzsignale code book and Enigma machine.

The documents captured from U-110 helped Bletchley Park codebreakers solve Reservehandverfahren, a reserve German hand cipher.

In 2007, the submarine's chronometer was featured on the BBC programme Antiques Roadshow, from Alnwick Castle, in the possession of the grandson of the captain of the ship which captured her.