The post of Führer der Unterseeboote (FdU) ("Leader of the U-boats") was the senior commanding officer of U-boat forces in a theatre of war.
The submarine service in the Kaiserliche Marine of World War I and the Kriegsmarine of World War II, used the title for several senior commands during those conflicts.
In 1917 the posts of FdU were themselves subordinated to an overall "Commander of the U-boats" (Befehlshaber der Unterseeboote, or BdU).
[1] The post of FdU was revived in the 1930s with German re-armament and was held from January 1936 and until 17 October 1939 by Karl Dönitz.
[2] In the further course of the war, several further posts were created for the commanders of U-boat regions In the further course of the war, several further posts were created for the commanders of U-boat regions.