O2

O2, O-2, o2, O2, O2, O2− or O2+ may refer to:

Science and technology

 * O2 or dioxygen, the common allotrope of the chemical element oxygen
 * O(2-), the ion oxide
 * O2-, the ion superoxide
 * O2+, the ion dioxygenyl
 * O(2+), doubly ionized oxygen
 * O2, an EEG electrode site according to the 10–20 system
 * SGI O2, a Unix workstation computer
 * UOC O2, institutional repository of the Open University of Catalonia
 * O2, the earliest defined spectral class for stars

Places

 * The O2, an entertainment district in London, England
 * The O2 Arena, the arena within The O2
 * O2 Arena (Prague) or Sazka Arena, an arena in Prague, Czech Republic
 * O2 Centre, an indoor shopping and entertainment centre on Finchley Road, London, England
 * O2 Residence, a part of the Jumeirah Lake Towers in Dubai, United Arab Emirates
 * O2 World (Berlin), an indoor arena in Berlin, Germany
 * O2 World (Hamburg), an indoor arena in Hamburg, Germany
 * Otoyol 2, a motorway in Turkey called "O2"
 * The O2 (Dublin), the former name of 3Arena
 * Ring 2 (Aarhus), a road in Aarhus, Denmark, which appears as "O2" on signs
 * Ring 2 (Copenhagen), a road in Copenhagen, Denmark, which appears as "O2" on signs

Film

 * Oxygen (2021 film) or O2, an American-French survival thriller film in production
 * O2 (2020 film), an Estonian-Latvia-Lithuanian-Finnish historical spy thriller film
 * O2 (2022 film), an Indian Tamil language survival thriller film

Albums

 * O2 (FireHouse album) (2000) album of the rock band FireHouse
 * O2 (O-Town album) (2002) album by American boy band O-Town
 * O2 (Tonéx album) (2002) album by Gospel singer Tonéx
 * O2: Avalon Remixed, a 2002 album by Avalon
 * O2 (Son of Dave album), 2006 album by Son of Dave

Songs

 * "O2", a song by Orange Range from Panic Fancy
 * "O2", a 2002 song by Sleater-Kinney from One Beat
 * "O2", a song by Suho from Self-Portrait

Other arts, entertainment, and media

 * Ö2, a radio service for Austria and South Tyrol
 * O2, a character in Kirby 64: The Crystal Shards

Businesses and organisations

 * O2, trading name for Telefónica Europe, a European telecommunications provider
 * O2 Store, a chain of retail stores owned and operated by Telefónica Europe, with regional subsidiaries:
 * O2 (brand), Telefónica mobile network global brand name
 * O2 (Ireland), merged into Three Ireland
 * O2 (UK)
 * O2 Czech Republic
 * Telefónica Germany
 * Telefónica Slovakia
 * O2 Academy, a chain of music venues
 * O2 Wireless USA or H2O Wireless, a prepaid wireless service by Locus Telecommunications
 * O2TV, a Russian independent socially political TV channel

Vehicles and vessels

 * Cessna O-2 Skymaster, a military twin-engine light aircraft
 * Douglas O-2, a military single-engine observation biplane
 * O 2-class submarine, a class of submarines of the Royal Netherlands Navy
 * Oldershaw O-2, a glider
 * SP&S Class O-2, a 1910 steam locomotives class
 * USS O-2 (SS-63), a 1918 United States O class submarine
 * Orbital O2, a tidal power turbine in Orkney
 * GNR Class O2, a class of British steam locomotives classified O2 by both the GNR and the LNER

Other uses

 * O-2, a pay grade in the US uniformed services
 * First lieutenant (United States) in the Army, Marine Corps, Air Force, and Space Force
 * Lieutenant (junior grade) in the Navy, Coast Guard, Public Health Service Commissioned Corps, and NOAA Commissioned Officer Corps