Führerhauptquartier Tannenberg (also known as "Installation T") was a Führer Headquarters built in 1939 for use as a military command and control facility by Adolf Hitler.

It was located near Freudenstadt and Hitler stayed there for a week in 1940 while inspecting the fortresses that formed the Maginot Line.

Tannenberg was constructed on Kniebis Mountain in the heart of the Black Forest on the grounds of an existing installation of Germany's western air defense zone near Freudenstadt.

[4] Hitler stayed at the Führerhauptquartier Tannenberg from 28 June to 5 July 1940, following the Fall of France, using it as a base from which to tour the fortresses of the Maginot Line.

[4] Tannenberg consisted of two concrete bunkers, one used as Hitler's private quarters and a second as a communications facility.