Oberstabsfeldwebel (OStFw or OSF, ) is the highest Non-commissioned officer (NCO) rank in German Army and German Air Force. It is grouped as OR-9 in NATO, equivalent to a sergeant major in the United States Army and a Warrant Officer Class 1 in the British Army. Attainment of this rank requires at least sixteen years since promotion to feldwebel and at least six years since promotion to hauptfeldwebel
In army/ air force context NCOs of this rank were formally addressed as Herr Oberstabsfeldwebel also informally / short Oberstaber.
The rank was introduced in the German Heer equivalent to the Marine grade Oberstabsbootsmann in 1955, and belongs to the grad group Unteroffiziere mit Portepee.
The rank is a comparatively new rank, and had not been used by any German military prior to in 1955. The Kriegsmarine, did however have a , used from 1939 to 1945.
The sequence of ranks (top-down approach) in that particular group (Senior NCOs with portepee) is as follows: