O6
# 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
