O1 or O-1 may refer to:
Aircraft
- O-1 Bird Dog, an observation aircraft manufactured by Cessna
- O-1 Curtiss Falcon, an observation aircraft manufactured by the Curtiss Aircraft Company
- O-1 Airship, an Italian manufactured semi-rigid airship operated by the US Navy
Music
- O1 (Hiroyuki Sawano album), 2015
- O1 (Son of Dave album), 2000
Military
- O-1 or fenrik, a second lieutenant rank in Norway
- The pay grade for ensign and second lieutenant ranks in the U.S. uniformed services
- USS O-1 (SS-62), lead ship of the United States O class submarines
- HNLMS O 1, a 1905 Royal Netherlands Navy O class submarine
Science and technology
- O1, or atomic oxygen
- O1 type star, a subclass of O-type star
- O-1 tool steel, a type of oil-hardening tool steel
- Haplogroup O1 (Y-DNA), a Y-DNA haplogroup
- O1: an EEG electrode site according to the 10–20 system
- O(1), time complexity expressed using Big O notation
- OpenAI o1, AI model released by OpenAI
Other
- O-1 visa, a variety of the U.S. O visa, allowing for temporary immigration for work purposes for individuals of extraordinary ability or achievement in certain areas
- Otoyol 1, a motorway in Turkey
- Ö1, an Austrian radio station
- O1 Communications, Inc., a California telecommunications company
- Orchestra ONE (O1), an experimental youth orchestra based in Maidstone, United Kingdom
- GNR Class O1, a class of British 2-8-0 steam locomotive designed by Nigel Gresley (later redesignated Class O3)
- LNER Thompson Class O1, a class of British 2-8-0 steam locomotive designed by Edward Thompson and rebuilt from Class O4
See also
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: