German submarine U-878 was a Type IXC/40 U-boat built for Nazi Germany's Kriegsmarine 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 shaft horsepower (1,010 PS; 750 kW) for use while submerged.

She was commissioned into service under the command of Kapitänleutnant Johannes Rodig (Crew 36) in 4th 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.