|Ordered||20 January 1941|
|Builder||DeSchiMAG AG Weser, Bremen|
|Laid down||20 June 1942|
|Launched||18 January 1943|
|Commissioned||1 May 1943|
|Fate||scuttled in position Coordinates: on 10 March 1944|
|Class and type||Type IXC/40 submarine|
|Height||9.60 m (31 ft 6 in)|
|Draught||4.67 m (15 ft 4 in)|
|Test depth||230 m (750 ft)|
|Complement||4 officers, 44 enlisted|
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-845 had a displacement of 1,144 tonnes (1,126 long tons) when at the surface and 1,257 tonnes (1,237 long tons) while submerged. The U-boat had a total length of 76.76 m (251 ft 10 in), a pressure hull length of 58.75 m (192 ft 9 in), a beam of 6.86 m (22 ft 6 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.67 m (15 ft 4 in). 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. She had two shafts and two 1.92 m (6 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 18.3 knots (33.9 km/h; 21.1 mph) and a maximum submerged speed of 7.3 knots (13.5 km/h; 8.4 mph). When submerged, the boat could operate for 63 nautical miles (117 km; 72 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 13,850 nautical miles (25,650 km; 15,940 mi) at 10 knots (19 km/h; 12 mph). U-845 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 180 rounds, and a 3.7 cm (1.5 in) SK C/30 as well as a 2 cm (0.79 in) C/30 anti-aircraft gun. The boat had a complement of forty-eight.
U-845 was ordered in January 1941 from DeSchiMAG AG Weser in Bremen under the yard number 1051. Her keel was laid down on 20 June 1942. The U-boat was launched the following year on 18 January 1943. she was commissioned into service under the command of Kapitänleutnant Udo Behrens (Crew 30) in 4th U-boat Flotilla on 1 May 1943.
On 10 July 1943 Rudolf Hoffmann (Crew 36) took over command. On her way to Gotenhafen U-845 assisted U-490 which was unable to dive and escorted her to port where they arrived on 24 July. Hoffmann handed over command to Werner Weber (Crew 25) in early October 1943. On 1 January 1944 U-845, which had been transferred to the 10th U-boat Flotilla, left for operations in the North Atlantic. Via Kristiansand, Stavanger and Bergen she reached her assigned operation area off Newfoundland in February 1944. A first attack on an unescorted freighter on 6 February 1944 failed, but three days later a British steamer, Kelmscott (7,039 GRT), fell victim to U-845's torpedo. On 14 February the U-boat was spotted by an aircraft. In the subsequent attack one crew member died and two others were wounded. An attack on another unescorted freighter the next day failed to sink the ship. On 10 March 1944, U-845 made contact with convoy SC 154, but was picked up by an escort, HMCS St. Laurent, in the late afternoon and depth-charged. When the U-boat surfaced late at night, she was attacked by St. Laurent and three other escorts of 9th Excort Group, HMCS Swansea, HMCS Owen Sound and HMS Forester, with artillery, killing Weber and the bridge crew as well as the crew servicing the AA guns. The rest of the crew survived the attack and was picked up by the escorts. Swansea picked up 23, Forester 17, and St. Laurent five men.