| U-3 | Type IIA |
| Feldpost Number | M 01 385 |
| Construction Yard | Deutsche Werke AG, Kiel-Gaarden |
| Yard Number | 238 |
| Ordered | 2nd Feb 1935 |
| Keel laid | 11th Feb 1935 |
| Launched | 19th Jul 1935 |
| Commissioned | 6th Aug 1935 |
| Baubelehrung | Marinelehr-und Reparaturwerkstatt, Kiel |
| Training, Flotillas and Duties |
| 08.35 - 06.40 | U-Schule Flottille, Neustadt Schulboot (training boat) Frontboot (operational)
|
| 07.40 - 07.44 | 21.U-Flottille, Pillau Schulboot (training boat)
|
| Commanders |
| 06.08.35 - 29.09.37 | OL ~ KL Hans Meckel see also: U-19 |
| 30.09.37 - 07.38 | OL Ernst-Günter Heinicke see also: U-51 U-53 |
| 29.10.38 - 02.01.40 | OL ~ KL Gustav Wilhelm Joachim Schepke see also: U-19 U-100 |
| 03.01.40 - 28.07.40 | KL Gerd Schreiber see also: U-95 |
| 29.07.40 - 10.11.40 | KL Helmut Franzke |
| 11.11.40 - 02.07.41 | KL Otto Erich August von Bülow see also: U-404 U-2545 |
| 03.07.41 - 02.03.42 | OL Hans-Hartwig Trojer see also: U-221 |
| 03.03.42 - 30.09.42 | OL Joachim Zander see also: U-311 |
| 01.10.42 - 18.05.43 | LT ~ OL Herbert Zoller see also: U-315 |
| 19.05.43 - 09.06.44 | LT ~ OL Ernst Hartmann see also: U-382 |
| 10.06.44 - 16.07.44 | LT Hermann Neumeister see also: U-291 |