| Old Rep at Birmingham Repertory Theatre | The Old Rep at Birmingham Repertory Theatre | England, Birmingham | 2013-03-14 | 2013-03-28 | 2013 | 1 | |
| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Allfarveg 7300 | 2012-11-11 | 2020-10-29 | 2012–2020 | 5 | |
| Ophelia Theater | Ophelia Theater | United States of America, Astoria, 21-12 30th Road | 2016-10-28 | 2016-11-13 | 2016 | 1 | |
| Orosháza | Orosháza | Hungary, Orosháza | 1890-05-12 | -- | 1890–1926 | 6 | |
| Opera House | Opera House | United States of America, Wyoming, Wyoming | -- | -- | | | |
| Opéra de Rouen | Opéra de Rouen | France, Rouen, 7 rue du Docteur Rambert | 2003-11-29 | 2003-11-30 | 2003 | 1 | |
| Orikkusu Gekijō | Orikkusu Gekijō (Orix Theater) | Japan, Osaka, 1-14-15 Shin-machi, Nishi-ku | 1971-10-03 | -- | 1971 | 2 | |
| On Pitch Performing Arts CenterOn Pitch Performing Arts Center | On Pitch Performing Arts Center | United States of America | 2023-09-15 | 2023-09-20 | 2023 | 1 | |
| Opera House | Opera House | United States of America, New Ulm | 1905-01-15 | 1905-01-15 | 1905 | 1 | |
| Opera Comique Theatre | Opera Comique Theatre | England, London | 1889-07-17 | 1895-03-30 | 1889–1895 | 6 | |
| Oosterpoort Groningen, De | De Oosterpoort Groningen | Netherlands, 9724 DA, Trompsingel 27, | 2000-04-20 | 2000-04-21 | 2000 | 1 | |
| Ouagadougou, Carrefour Internationale de Théâtre de Ouagadougou | Carrefour Internationale de Théâtre de Ouagadougou | Burkina Faso, Bilbalogho, Ouagadougou, Burkina Faso | 2002-07-13 | -- | 2002 | 1 | |
| Omaha | Omaha | United States of America, Omaha | 1903-11-05 | 1903-11-05 | 1903 | 1 | |
| Orăștie | Orăștie | Romania, Orăștie | 1911-02-16 | -- | 1911 | 1 | |
| Odenkirchen | Odenkirchen | Germany, Odenkirchen | 1893-10-07 | -- | 1893 | 1 | |
| Ovalhouse | Ovalhouse | England, London, 52-54 Kennington Oval | 2018-05-17 | 2018-05-19 | 2018 | 1 | |
| Olten | Olten | Switzerland, Olten | 2003-02-17 | -- | 2003 | 1 | |
| Oakland University | Oakland University | United States of America, Rochester, 2200 North Squirrel Road | 1972-03-02 | 1972-03-26 | 1972 | 1 | |
| Opera House | Opera House | United States of America, Dixon | 1904-11-30 | 1907-12-21 | 1904–1907 | 2 | |
| Opernhaus Hannover | Opernhaus Hannover | Germany, Hannover, Opernplatz 1 | 1928-03-06 | 1956-12-05 | 1928–1956 | 2 | |
| Opera House | Opera House | United States of America, Kentucky, Kentucky | 1899-12-20 | 1903-12-10 | 1899–1903 | 2 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Otta Samfunnshus | Otta Samfunnshus | Norway, Otta, Klyphaugvegen 8, 2670 Otta | 1973-09-30 | -- | 1973–1987 | 4 | |
| Oblasni dram teatr | Oblasni dram teatr | Russia, Kaliningrad, Prospekt Mira, 4 | 1960-01- | -- | 1960–1973 | 2 | |
| Osnabrücker Stadttheater | Osnabrücker Stadttheater | Germany, Osnabrück, Große Gildewart 7 | 1894-03-29 | 1900-04-26 | 1894–1909 | 7 | |
| Oldenburgisches Staatstheater | Oldenburgisches Staatstheater | Germany, Oldenburg, Theaterwall 28 | 1918-11-30 | 2015-12-20 | 1918–2015 | 12 | |
| Ohgawara | Ohgawara | Japan, Ohgawara | -- | -- | | | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo | 1994-08-23 | -- | 1994 | 1 | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Oseberg Kulturhus | Oseberg Kulturhus | Norway, Tønsberg, Ollebukta 3 | 2008-03-08 | 2008-10-10 | 2008–2009 | 3 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Osses, Théâtre des | Théâtre des Osses | Switzerland, Givisiez, Place des Osses 1 | 2011-02-10 | 2011-02-27 | 2011 | 1 | |
| Ontmoetingscentrum d'Iefte | Ontmoetingscentrum d'Iefte | Belgium, Deerlijk, Hoogstraat 122 | 2002-01-14 | 2002-01-15 | 2002 | 1 | |
| Odense | Odense | Denmark, Odense | 1948-04-20 | -- | 1948–2000 | 2 | |
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