O3

O3 may refer to:

O₃, the molecular formula for ozone
O³⁻, the ozonide anion
O(3), the 3-dimensional orthogonal group in group theory
O₃, the 1993 debut album by the techno band Sunscreem
O3 A Trilogy, a 2008 concept album trilogy by progressive metal band Dominici
O3 star, in stellar classification, a subclass of type O stars
O-3, the pay grade for the following officer ranks in the U.S. uniformed services:
- Captain in the Army, Marine Corps, Air Force, and Space Force
- Lieutenant in the Navy, Coast Guard, Public Health Service Commissioned Corps, and NOAA Commissioned Officer Corps
Haplogroup O3 (Y-DNA), a Y-DNA Haplogroup
Oldershaw O-3, glider
USS O-3 (SS-64), a 1917 United States O class submarine
Otoyol 3, a Turkish motorway from Edirne to Istanbul
Oskarshamn 3, unit 3 at Oskarshamn Nuclear Power Plant in Sweden
O3 (album), a 2008 album by Son of Dave
LNER Class O3, a class of British steam locomotives

See also