German submarine U-107 was a Type IXB U-boat of Nazi Germany's Kriegsmarine that operated during World War II. Between January 1941 and August 1944, she sailed on 13 active patrols at a time when a U-boat averaged a lifespan of seven to ten patrols. During that time, U-107 sank 39 Allied ships and damaged four. The U-boat was launched on 2 July 1940, based at the U-boat port of Lorient, with a crew of 53 under the initial command of Günter Hessler. She was later commanded, in order, by Harald Gelhaus, Valker Simmermacher and her final commander, Karl Heinz Fritz.
Type IXB submarines were slightly larger than the original Type IX submarines, later designated IXA. U-107 had a displacement of when at the surface and while submerged. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-107 was fitted with six torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one SK C/32 naval gun, 180 rounds, and a SK C/30 as well as a C/30 anti-aircraft gun. The boat had a complement of forty-eight.
On 16 August 1944, U-107 departed from Lorient on a transport run to La Pallice. She was intercepted on 18 August in the Bay of Biscay, west of La Rochelle, in position , by Allied forces, and was sunk by depth charges from a Short Sunderland (serialEJ150) of No. 201 Squadron, Royal Air Force. All 58 hands were lost.
U-107 took part in 15 wolfpacks, namely: