| Opernhaus | Opernhaus | Germany, Wuppertal, Kurt-Drees-Straße 4 | 2011-06-26 | 2011-12-01 | 2011 | 2 | |
| Oskar-Herbig-Halle | Oskar-Herbig-Halle | Germany, Mellrichstadt, Bahnhofstr. 17 | 2004-03-03 | -- | 2004–2011 | 2 | |
| Opéra Orchestre national Montpellier Occitanie | Opéra Orchestre national Montpellier Occitanie | France, Montpellier, 11 Boulevard Victor Hugo | 2018-01-12 | 2018-01-13 | 2018 | 1 | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Opera House | Opera House | United States, Detroit | 1896-02-18 | 1910-09-28 | 1896–1910 | 2 | |
| O'Connell Theatre | O'Connell Theatre | United States, Dekalb, Stevens Building, School of Theatre and Dance Northern Illinois University | 2009-02-19 | 2009-03-01 | 2009 | 1 | |
| Obshtinski teatar Vazrazhdane | Obshtinski teatar Vazrazhdane | Bulgaria, Sofia, Sq. Petko Slaveykov 4 (пл. Петко Р. Славейков 4) | 1996-11-30 | -- | 1996 | 1 | |
| Odéon-Théâtre de l'Europe | Odéon-Théâtre de l'Europe | France, Paris, 67 Rue Monsieur le Prince | 1993-03-12 | 2019-06-15 | 1993–2019 | 5 | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Opernhaus | Opernhaus | Germany, Frankfurt, Opernplatz 1 | 1892-12-10 | -- | 1892–1940 | 2 | |
| Oerlenbach | Oerlenbach | Germany, Oerlenbach | 2009-12-19 | -- | 2009 | 1 | |
| OC De Buiting | OC De Buiting (Cultuur, gemeenschaps of ontmoetingscentrum) | Belgium, Beringen, Tessenderlosesteenweg 18 | 2007-11-29 | 2007-11-30 | 2007 | 1 | |
| Odense Theater | Odense Theater | Denmark, Odense, Sortebrødre Torv | 1876-04-20 | 1899-10-20 | 1876–1901 | 9 | |
| Opéra-Théâtre de Limoges | Opéra-Théâtre de Limoges | France, Limoges, 48 rue Jean Jaurès | 2017-05-09 | 2017-05-11 | 2017 | 1 | |
| Oakland University | Oakland University | United States, Rochester, 2200 North Squirrel Road | 1972-03-02 | 1972-03-26 | 1972 | 1 | |
| Ovalhouse | Ovalhouse | England, London, 52-54 Kennington Oval | 2018-05-17 | 2018-05-19 | 2018 | 1 | |
| Opernhaus | Opernhaus | Germany, Essen | 1942-04-19 | -- | 1942 | 1 | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Odeon de Spiegel | Odeon de Spiegel | Netherlands, Zwolle, Blijmarkt 25 | 2000-04-28 | -- | 2000–2008 | 2 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Ophelia Theater | Ophelia Theater | United States, Astoria, 21-12 30th Road | 2016-10-28 | 2016-11-13 | 2016 | 1 | |
| Opera House | Opera House | United States, New Ulm | 1905-01-15 | 1905-01-15 | 1905 | 1 | |
| Open Space Theatre | Open Space Theatre | United States, New York | 1982-01-11 | -- | 1982 | 1 | |
| Omaha | Omaha | United States, Omaha | 1903-11-05 | 1903-11-05 | 1903 | 1 | |
| OC Westrand | OC Westrand | Belgium, Dilbeek, Kamerijklaan z/n | 1994-04-14 | -- | 1994–2004 | 4 | |
| Opéra de Rouen | Opéra de Rouen | France, Rouen, 7 rue du Docteur Rambert | 2003-11-29 | 2003-11-30 | 2003 | 1 | |
| Oblasni dram teatr | Oblasni dram teatr | Russia, Kaliningrad, Prospekt Mira, 4 | 1960-01- | -- | 1960–1973 | 2 | |
| Oseberg Kulturhus | Oseberg Kulturhus | Norway, Tønsberg, Ollebukta 3 | 2008-03-08 | 2008-10-10 | 2008–2009 | 3 | |
| Orkanger | Orkanger | Norway, Orkanger | 1958-01-23 | -- | 1958–2005 | 5 | |
| Olympia Theatre | Olympia Theatre | Ireland, Dublin, 72 Dame St | 1954-07-05 | -- | 1954 | 1 | |
| Olten | Olten | Switzerland, Olten | 2003-02-17 | -- | 2003 | 1 | |
| Osses, Théâtre des | Théâtre des Osses | Switzerland, Givisiez, Place des Osses 1 | 2011-02-10 | 2011-02-27 | 2011 | 1 | |
| Oslo fengsel | Oslo fengsel | Norway, Oslo, Åkebergveien 11 | 2012-11-27 | -- | 2012 | 2 | |
| Old Red Lion Theatre | Old Red Lion Theatre | England, London, 418 St John Street | 2000-10-17 | 2000-11-11 | 2000 | 1 | |
| Opera House | Opera House | United States, Dixon | 1904-11-30 | 1907-12-21 | 1904–1907 | 2 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Oslo Nye Trikkestallen | Oslo Nye Trikkestallen | Norway, Oslo, Torshovgata 33 | 2011-07-01 | 2019-01-06 | 2011–2019 | 2 | |
| Osnabrücker Stadttheater | Osnabrücker Stadttheater | Germany, Osnabrück, Große Gildewart 7 | 1894-03-29 | 1900-04-26 | 1894–1909 | 7 | |
| Oviedo | Oviedo | Spain | 1904-- | -- | 1904 | 1 | |
| Oskarshamn | Oskarshamn | Sweden, Oskarshamn | 1991-05-03 | 1991-05-03 | 1991–1992 | 2 | |
| Odin Teatret | Odin Teatret | Denmark, Holstebro, Særkærparken 144 | 2011-- | -- | 2011–2016 | 4 | |
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