| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Ocna Sibiului | Ocna Sibiului | Romania, Ocna Sibiului | -- | -- | | | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Ogra | Ogra | Romania, Ogra | -- | -- | | | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Ostrava | Ostrava | Czech Republic, Ostrava | -- | -- | | | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Opera House | Opera House | United States, Telluride | -- | -- | | | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Opole | Opole | Poland, Opole | -- | -- | | | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Obldramteatr | Obldramteatr | Russia, Ivanovo | 1940-03-24 | -- | 1940 | 1 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| Opera House | Opera House | United States, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| Opera House | Opera House | United States, Concord | 1909-04-22 | 1909-04-22 | 1909 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Opéra de Dijon | Opéra de Dijon | France, Dijon, 11 Boulevard de Verdun | 2014-03-10 | 2014-03-12 | 2014 | 1 | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo, Rosenkrantz' gate 10 | 1994-08-23 | -- | 1994 | 1 | |
| Överkalix Folkets Hus | Överkalix Folkets Hus | Sweden, Överkalix, Bulandsgatan 2 | 2010-11-16 | -- | 2010 | 1 | |
| Oslo dagene, Akershus Festning | Oslo dagene, Akershus Festning | Norway, Oslo | 1983-08-29 | 1983-09-03 | 1983 | 1 | |
| Opera House | Opera House | United States, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Opera House | Opera House | United States, Pensacola | 1903-10-25 | 1903-10-25 | 1903 | 1 | |
| O'Reilly Theatre | O'Reilly Theatre | Ireland, Dublin, Great Denmark Street | 2011-09-27 | 2011-10-16 | 2011 | 1 | |
| Olavskapellet, Borgarsyssel Museum | Olavskapellet, Borgarsyssel Museum | Norway, Sarpsborg, Gamlebygaten 8 | 2006-08-01 | 2006-08-02 | 2006 | 1 | |
| Oblastnoi dramteatr Volgograd | Oblastnoi dramteatr Volgograd | Russia, Volgograd | 1948-10- | -- | 1948 | 1 | |
| OPERATTEN im STATTtheater | OPERATTEN im STATTtheater | Switzerland, Stäfa, Bahnhofstrasse 52 | 2007-03-07 | 2007-04-21 | 2007 | 1 | |
| Ottumwa | Ottumwa | United States, Ottumwa | 1903-11-04 | 1903-11-04 | 1903 | 1 | |
| Opera House | Opera House | United States, New Castle | 1907-03-09 | 1907-03-09 | 1907 | 1 | |
| Old globe theatre, the | The Old Globe Theatre | United States, San Diego, 1363 Old Globe Way | 1995-04-30 | 1995-06-18 | 1995 | 1 | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Ottawa Little Theatre Group | Ottawa Little Theatre Group | Canada, Ottawa | 1945-12-20 | -- | 1945 | 1 | |
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