| U-78 | Type VIIC |
| Feldpost Number | M 29 850 |
| Construction Yard | Vulkan Vegesack Werft, Bremen |
| Yard Number | 6 |
| Ordered | 25th Jan 1939 |
| Keel laid | 28th Mar 1940 |
| Launched | 7th Dec 1940 |
| Commissioned | 15th Feb 1941 |
| Baubelehrung | Baubelehrung U-Boote Nordsee, Bremen |
| Training, Flotillas and Duties |
| 02.41 - 03.45 | 22.U-Flottille, Gotenhafen Schulboot (training boat)
|
| 03.45 - 04.45 | 4.U-Flottille, Stettin Stromboot (used as power generator)
|
| Commanders |
| 02.41 - 07.41 | KL Alfred Dumrese see also: U-655 |
| 07.41 - 02.42 | OL Kurt Makowski see also: U-619 |
| 02.42 - 07.42 | OL Max Dieterich see also: U-637 |
| 07.42 - 11.42 | KL Ernst Ziehm see also: U-232 |
| 11.42 - 05.43 | KL Helmut Sommer see also: U-139 U-853 |
| 05.43 - 11.44 | OL Wilhelm Eisele see also: U-57 U-1103 |
| 11.44 - 04.45 | OL Horst Hübsch see also: U-145 |