U-boat Flotillas
There were thirty U-boat flotillas created by the Kriegsmarine between 1935 and 1945. Each flotilla was of an indeterminate size that depended on a combination of circumstances and conditions of U-boat deployment. Flotilla command provided an administrative framework under which to operate U-boats at sea. Combat U-boats were not under operational control of their flotilla command however - BdU continued to oversee the coordination of the U-boat campaign against the Allies.Combat Flotillas
| 1st U-Flotilla | 2nd U-Flotilla | 3rd U-Flotilla | 6th U-Flotilla* | 7th U-Flotilla |
| 9th U-Flotilla | 10th U-Flotilla | 11th U-Flotilla | 12th U-Flotilla | 13th U-Flotilla |
| 14th U-Flotilla | 18th U-Flotilla | 23rd U-Flotilla** | 29th U-Flotilla | 30th U-Flotilla |
| 33rd U-Flotilla | ||||
Training Flotillas
| 4th U-Flotilla | 5th U-Flotilla | 6th U-Flotilla* | 8th U-Flotilla | 19th U-Flotilla |
| 20th U-Flotilla | 21st U-Flotilla | 22nd U-Flotilla | 23rd U-Flotilla** | 24th U-Flotilla |
| 25th U-Flotilla | 26th U-Flotilla | 27th U-Flotilla | 31st U-Flotilla | 32nd U-Flotilla |
*This flotilla was stationed in both Danzig (training)and Sainte Nazaire (combat) until mid -1942 when it became totally front-line.
**This flotilla was on combat status between September 1941 and May 1942. From August 1943 to March 1945 it was relegated to Baltic training.