| Opole | Opole | Poland, Opole | -- | -- | | | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Ostrava | Ostrava | Czech Republic, Ostrava | -- | -- | | | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Ocna Sibiului | Ocna Sibiului | Romania, Ocna Sibiului | -- | -- | | | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Ogra | Ogra | Romania, Ogra | -- | -- | | | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Opera House | Opera House | United States, Telluride | -- | -- | | | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Oberammergau, Passionstheater | Passionstheater Oberammergau | Germany, Oberammergau, Othmar-Weis-Str. | 2016-07-01 | 2016-07-23 | 2016 | 1 | |
| Örkény István Színház | Örkény István Színház | Hungary, Budapest, Madách Imre tér 6 | 2012-03-17 | -- | 2012 | 1 | |
| Obergrafschaft, Theater der | Theater der Obergrafschaft | Germany, Schüttorf, Hermann-Schlikker-Str. 1-3 | 2015-10-03 | -- | 2015 | 1 | |
| Osobnyak Theatre | Osobnyak Theatre | Russia, St. Petersburg, Kamennoostrovsky 55 | 2011-05-15 | 2011-05-17 | 2011 | 1 | |
| Opera House | Opera House | United States, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| Open Space Theatre | Open Space Theatre | United States, New York | 1982-01-11 | -- | 1982 | 1 | |
| Old Rep at Birmingham Repertory Theatre | The Old Rep at Birmingham Repertory Theatre | England, Birmingham | 2013-03-14 | 2013-03-28 | 2013 | 1 | |
| Officina Giovani - Cantieri Culturali Ex Macelli | Officina Giovani - Cantieri Culturali Ex Macelli | Italy, Prato, Piazza Macelli, 4 | 2007-04-21 | -- | 2007 | 1 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 1 | |
| Off Latina | Off Latina | Spain, Madrid, Calle de los Mancebos, 4 | 2019-11-07 | 2020-04-29 | 2019 | 1 | |
| Ostseebad Göhren | Ostseebad Göhren | Germany, Göhren | 2010-05-04 | -- | 2010 | 1 | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Oosterpoort Groningen, De | De Oosterpoort Groningen | Netherlands, 9724 DA, Trompsingel 27, | 2000-04-20 | 2000-04-21 | 2000 | 1 | |
| Ontmoetingscentrum 't Waaigat | Ontmoetingscentrum 't Waaigat | Belgium, Zwijndrecht, Kerkplein 1 | 2003-05-06 | 2003-05-06 | 2003 | 1 | |
| Obldramteatr | Obldramteatr | Russia, Ivanovo | 1940-03-24 | -- | 1940 | 1 | |
| Opéra de Dijon | Opéra de Dijon | France, Dijon, 11 Boulevard de Verdun | 2014-03-10 | 2014-03-12 | 2014 | 1 | |
| Ovågen | Ovågen | Norway, Øygarden | 2005-09-04 | -- | 2005 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Orpheum Theatre | Orpheum Theatre | United States, Salt Lake City | 1908-06-13 | 1908-06-13 | 1908 | 1 | |
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