Please read the information about this list on User:SirJective/Parenthesis before working with it!

• O'Day (crater) - O'Day
• O My Father (hymn) - O My Father
• Oberkampf (Paris Metro) - Oberkampf
• Observation tower (ride) - Observation tower
• Obstruction (baseball) - Obstruction
• Occasional Conformity Act (1711) - Occasional Conformity Act
• Odéon (Paris Metro) - Odéon
• Offensive philosophy (American football) - Offensive philosophy
• Office of the Military Advisor to the Commonwealth Government (Philippines) (r) - Office of the Military Advisor to the Commonwealth Government
• Official Opposition Shadow Cabinet (Australia) - Official Opposition Shadow Cabinet
• Official Opposition Shadow Cabinet (Canada) - Official Opposition Shadow Cabinet
• Official Opposition Shadow Cabinet (UK) - Official Opposition Shadow Cabinet
• Offside law (football) - Offside law
• Ogawa, Ibararaki (Higashiibaraki) - Ogawa, Ibararaki
• Oh Brother, Where Art Thou? (soundtrack) (r) - Oh Brother, Where Art Thou?
• Olbers (crater) - Olbers
• Old Harrison County Courthouse (Texas) - Old Harrison County Courthouse
• Old Major (Animal Farm) - Old Major
• Old Post Office Building (Washington) - Old Post Office Building
• Old Trick New Dog (album) - Old Trick New Dog
• Old Woman River (Ontario) - Old Woman River
• Olde Cheshire Cheese (London pub) - Olde Cheshire Cheese
• Olivia (Buffy the Vampire Slayer) - Olivia
• Olpe (district) - Olpe
• Olympic athletics medalists (men) (r) - Olympic athletics medalists
• Olympic athletics medalists (women) (r) - Olympic athletics medalists
• Olympic Baseball Center (Athens) (r) - Olympic Baseball Center
• Olympic Baseball Centre (Athens) - Olympic Baseball Centre
• Olympic medalists in athletics (men) - Olympic medalists in athletics
• Olympic medalists in athletics (women) - Olympic medalists in athletics
• Olympic medalists in swimming (men) - Olympic medalists in swimming
• Olympic Softball Stadium (Athens) - Olympic Softball Stadium
• Olympus Spaceport (Orbiter sim) - Olympus Spaceport
• Omega, (Navigation System) (r) - Omega,
• On the Town with The League of Gentlemen (radio series) (r) - On the Town with The League of Gentlemen
• One From the Heart (album) - One From the Heart
• One pair (poker) - One pair
• One pair (Poker) (r) - One pair
• Onega (disambiguation) - Onega
• Opel RAK.1 (plane) - Opel RAK.1
• Open Range (movie) - Open Range
• Operation Gothic Serpent timeline (Somalia, 1993) (r) - Operation Gothic Serpent timeline
• Operation Tsunami (Canada) - Operation Tsunami
• Opiuchus (planet) (r) - Opiuchus
• Opposition House Leader (Canada) (r) - Opposition House Leader
• Optimize (magazine) - Optimize
• Opéra (Paris Metro) - Opéra
• Opus 64 No 1 (Chopin) (r) - Opus 64 No 1
• Opuwo (Constituency) - Opuwo
• Ordinary (heraldry) - Ordinary
• Oregon Ballot Measure 11 (1994) - Oregon Ballot Measure 11
• Oregon Ballot Measure 16 (1994) - Oregon Ballot Measure 16
• Oregon Ballot Measure 25 (2002) - Oregon Ballot Measure 25
• Oregon Ballot Measure 27 (2002) - Oregon Ballot Measure 27
• Oregon Ballot Measure 28 (2003) - Oregon Ballot Measure 28
• Oregon Ballot Measure 30 (2004) - Oregon Ballot Measure 30
• Oregon Ballot Measure 36 (1996) - Oregon Ballot Measure 36
• Oregon Ballot Measure 47 (1996) - Oregon Ballot Measure 47
• Oregon Ballot Measure 5 (1990) - Oregon Ballot Measure 5
• Oregon Ballot Measure 50 (1997) - Oregon Ballot Measure 50
• Oregon Ballot Measure 51 (1997) - Oregon Ballot Measure 51
• Oregon Ballot Measure 60 (1998) - Oregon Ballot Measure 60
• Oregon Ballot Measure 9 (1992) - Oregon Ballot Measure 9
• Oregon Delegation in 107th &/or 108th Congress (2001-2005) - Oregon Delegation in 107th &/or 108th Congress
• Organizing Committee of Principist Trotskyism (Fourth International) - Organizing Committee of Principist Trotskyism
• Organizing Committee, Communist Party of India (Marxist-Leninist) - Organizing Committee, Communist Party of India
• Orishas (band) - Orishas
• Orontius (crater) - Orontius
• Orsay Ville (Paris Metro) - Orsay Ville
• Orthosie (moon) - Orthosie
• Osteopetrosis, (generic term) - Osteopetrosis,
• Osterode (district) - Osterode
• Otter island (fictional) - Otter island
• Our Classbook (Twins album) (r) - Our Classbook
• Our Classbook (Twins) (r) - Our Classbook
• Ourcq (Paris Metro) - Ourcq
• Outpost (computer game) - Outpost
• Outsider (Known Space) - Outsider
• Oyggjaframi (m-l) - Oyggjaframi
• Oyggjaframji (m-l) (r) - Oyggjaframji