|21st U-boat Flotilla|
|Engagements||World War II|
21st U-boat Flotilla ("21. Unterseebootsflottille") was a unit of Nazi Germany's Kriegsmarine before and during World War II. It was formed in 1935 as a Schulverband ("School Unit") based at Kiel under the command of Kapitän zur See Kurt Slevogt (Chef des Schulverbandes).
- Kapitän zur See Kurt Slevogt (1935—1937)
- Kapitänleutnant Heinz Beduhn (November 1937—March 1940)
- Korvettenkapitän Paul Büchel (March 1940—June 1943)
- Korvettenkapitän Otto Schuhart (June 1943—September 1944)
- Kapitänleutnant Herwig Collmann (September 1944—March 1945)
Fifty-one U-boats were assigned to this flotilla during its service.