O3 may refer to:
Science and technology
- Ozone (O3), an allotrope of oxygen
- O, the ozonide anion
- O(3), the 3-dimensional orthogonal group in group theory
- O3 star, in stellar classification, a subclass of type O stars
- Haplogroup O3 (Y-DNA), a Y-DNA Haplogroup
- OpenAI o3, an artificial intelligence model by OpenAI
Music
- O3, the 1993 debut album by the techno band Sunscreem
- O3 A Trilogy, a 2008 concept album trilogy by progressive metal band Dominici
- O3 (album), a 2008 album by Son of Dave
Military
- O-3, a uniformed services pay grade of the United States for the following:
- Captain (United States O-3), in the Army, Marine Corps, Air Force, and Space Force
- Lieutenant (navy), in the Navy, Coast Guard, Public Health Service Commissioned Corps, and NOAA Commissioned Officer Corps
- USS O-3 (SS-64), a 1917 United States O class submarine
Transportation
- Oldershaw O-3, a glider
- Otoyol 3, a Turkish motorway from Edirne to Istanbul
- LNER Class O3, a class of British steam locomotives
Other uses
- Oskarshamn 3, unit 3 at Oskarshamn Nuclear Power Plant in Sweden
See also
- 03 (disambiguation)
- Ö3, Austrian radio station
- 3O (disambiguation)
Topics referred to by the same termThis disambiguation page lists articles associated with the same title formed as a letter–number combination.If an internal link led you here, you may wish to change the link to point directly to the intended article. Category: