| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Ocna Sibiului | Ocna Sibiului | Romania, Ocna Sibiului | -- | -- | | | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Ohgawara | Ohgawara | Japan, Ohgawara | -- | -- | | | |
| Ogra | Ogra | Romania, Ogra | -- | -- | | | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Opole | Opole | Poland, Opole | -- | -- | | | |
| Opera House | Opera House | United States of America, Wyoming, Wyoming | -- | -- | | | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Opera House | Opera House | United States of America, Telluride | -- | -- | | | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo | 1994-08-23 | -- | 1994 | 1 | |
| Odéon Théâtre de l'Europe | Odéon Théâtre de l'Europe | France, 75006 Paris, Place de l'Odéon | 2023-05-12 | 2023-06-09 | 2023 | 1 | |
| Odeïon | Odeïon | Austria, Salzburg/Langwied, Waldorfstraße 13 | 2013-09-26 | 2013-10-27 | 2013 | 1 | |
| Odda ungdomsskole | Odda ungdomsskole | Norway, Odda, Eidesmoen | 2006-11-15 | -- | 2006 | 1 | |
| Overholser Theatre | Overholser Theatre | United States of America, Ardmore | 1910-12-21 | 1910-12-21 | 1910 | 1 | |
| Opera House | Opera House | United States of America, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Oslo Rådhus | Oslo Rådhus | Norway, Oslo, Rådhusplassen 1 | 2009-03-28 | -- | 2009 | 1 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| Oslo Public Library | Oslo Public Library | Norway, Oslo, Arne Garborgs plass 4 | 1988-06-30 | -- | 1988 | 1 | |
| Opera House | Opera House | United States of America, Concord | 1909-04-22 | 1909-04-22 | 1909 | 1 | |
| Oblastnoi dramatičeskij teatr | Oblastnoi dramatičeskij teatr | Russia, Veliky Novgorod | 1948-09- | -- | 1948 | 1 | |
| Oddemarka skole | Oddemarka skole | Norway, Kristiansand, Kristiansand | 2006-11-08 | -- | 2006 | 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 of America, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Open Scene Orlando (Instagram) | Open Scene Orlando (Instagram) | United States of America, Orlando | 2020-05-07 | 2020-06-10 | 2020 | 1 | |
| Opéra national du Rhin | Opéra national du Rhin | France, Strasbourg, 19 place Broglie | 2020-09-19 | 2020-09-20 | 2020 | 1 | |
| O'Reilly Theatre | O'Reilly Theatre | Ireland, Dublin, Great Denmark Street | 2011-09-27 | 2011-10-16 | 2011 | 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 | |
| Orăștie | Orăștie | Romania, Orăștie | 1911-02-16 | -- | 1911 | 1 | |
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