|Ordered||2 April 1942|
|Builder||DeSchiMAG AG Weser, Bremen|
|Laid down||16 June 1943|
|Launched||6 January 1944|
|Commissioned||14 April 1944|
|Fate||sunk by depth charges from British warships at Coordinates: on 10 April 1945|
|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|
|Identification codes:||M 00 518|
|Commanders:||Kptlt. Hans-Joachim Brans|
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-878 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-878 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) Flak M42 as well as two twin 2 cm (0.79 in) C/30 anti-aircraft guns. The boat had a complement of forty-eight.
U-878 was ordered in April 1942 from DeSchiMAG AG Weser in Bremen under the yard number 1086. Her keel was laid down on 16 June 1943 and the U-boat was launched the following year on 6 January 1944. She was commissioned into service under the command of Kapitänleutnant Johannes Rodig (Crew 36) in 4th U-boat Flotilla.
After completing training and work up for deployment, U-878 was transferred to the 33rd U-boat Flotilla. Her first war patrol was a supply run for the beleaguered U-boat base of St. Nazaire. The U-boat left Horten Naval Base on 9 February 1945 and arrived at her destination on 20 March. On the return leg, she was picked up by escorts of convoy ONA 265 on 10 April 1945. HMS Vanquisher and HMS Tintagel Castle attacked U-878 with depth charges and squid mortar. U-878 was sunk in position , all 51 crew members were lost.