Fritz Erich Fellgiebel (4 October 1886 – 4 September 1944) was an anti-Nazi German Army general and a conspirator in the 20 July plot to assassinate Nazi dictator Adolf Hitler.
In 1929, Fellgiebel became head of the (German: Chiffrierstelle) cipher bureau of the Reichswehrministerium, which would eventually become the OKW/Chi.
He was a signals specialist and was instrumental in introducing a common enciphering machine, the Enigma machine.
However, he was unsuccessful in promoting a single cipher agency to coordinate all operations, as was demanded by OKW/Chi and was still blocked by Joachim von Ribbentrop, Heinrich Himmler and Hermann Göring until autumn 1943.
It was not achieved until General Albert Praun took over the post.