Oberstabsbootsmann (OStBtsm or OSB) is the highest Non-commissioned officer (NCO) rank in the German Navy. It is grouped as OR9 in NATO, equivalent to a Master Chief Petty Officer in the United States Navy, and a Warrant Officer Class 1 in the British Royal Navy. In Navy context, NCOs of this rank were formally addressed as Herr/ Frau Oberstabsbootsmann also informally/ short Oberstaber. The rank was introduced in the German Navy equivalent to the German Heer and German Luftwaffe grad Oberstabsfeldwebel in 1995, and belongs to the grad group Unteroffiziere mit Portepee. See also