| Date | U-boat | Crew | Dead | Surv. | Notes | |
January | ||||||
| 30 Jan, 1940 | U-15 | + | 25 | 25 | 0 | |
| 30 Jan, 1940 | U-55 | 42 | 1 | 41 | Aircraft & warship | |
February | ||||||
| 5 Feb, 1940 | U-41 | + | 49 | 49 | 0 | Warship |
| 12 Feb, 1940 | U-33 | 42 | 25 | 17 | Lost to mines | |
| 20 Feb, 1940 | U-54 | + | 41 | 41 | 0 | Missing. Lost to mines |
| 23 Feb, 1940 | U-53 | + | 42 | 42 | 0 | Warship |
| 25 Feb, 1940 | U-63 | 25 | 1 | 24 | Warship | |
March | ||||||
| 11 Mar, 1940 | U-31 | + | 58 | 58 | 0 | Aircraft |
| 13 Mar, 1940 | U-44 | + | 47 | 47 | 0 | Lost to minesWarship |
| 27 Mar, 1940 | U-22 | + | 27 | 27 | 0 | Missing. Lost to mines |
April | ||||||
| 6 Apr, 1940 | U-1 | + | 24 | 24 | 0 | Missing. Lost to mines |
| 6 Apr, 1940 | U-50 | + | 44 | 44 | 0 | Lost to mines |
| 13 Apr, 1940 | U-64 | 46 | 8 | 38 | Aircraft | |
| 15 Apr, 1940 | U-49 | 42 | 1 | 41 | Warship | |
May | ||||||
| 31 May, 1940 | U-13 | 26 | 0 | 26 | Warship | |
June | ||||||
| 22 Jun, 1940 | U-122 | + | 49 | 49 | 0 | Missing. |
July | ||||||
| 1 Jul, 1940 | U-26 | 48 | 0 | 48 | Scuttled by its own crew | |
| 1 Jul, 1940 | U-102 | + | 43 | 43 | 0 | Warship |
August | ||||||
| 1 Aug, 1940 | U-25 | + | 49 | 49 | 0 | Lost to mines |
| 20 Aug, 1940 | U-51 | + | 43 | 43 | 0 | Warship |
September | ||||||
| 3 Sep, 1940 | U-57 | 25 | 6 | 19 | ||
October | ||||||
| 30 Oct, 1940 | U-32 | 42 | 9 | 33 | Warship | |
November | ||||||
| 2 Nov, 1940 | U-31 | 46 | 2 | 44 | Warship | |
| 28 Nov, 1940 | U-104 | + | 49 | 49 | 0 | Missing. |
23 U-boats lost in 1940 (643 men died and 331 men survived those losses)
+ means that the boat was lost with all hands.
U-boats stricken from records (often after sustaining prior combat damage) and boats scuttled by their own crews are not included in this losses figure here above. We, however, include them in the listing for better view of events.

