O6

O6 or O-6 may refer to:

LNER Class O6, a class of British steam locomotives
O6 star, a subclass of O-class stars
OceanAir IATA airline designator
O-6, a pay grade in the US uniformed services:
Colonel in the Army, Marine Corps, Air Force, and Space Force
Captain in the Navy, Coast Guard, Public Health Service Commissioned Corps, and NOAA Commissioned Officer Corps
the "Occupied 6", an Irish republican euphemism for Northern Ireland
USS O-6 (SS-67), an O-class submarine of the United States Navy
Otoyol 6, a motorway in Turkey

See also