| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
| Odd Duck Studio | Odd Duck Studio | United States of America, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| Opština Bečej | Opština Bečej | Serbia, Opština Bečej | 1903-03-11 | -- | 1903 | 1 | |
| OSCO - Open Space Hannover | OSCO - Open Space Hannover | Germany, Hannover, Fössestraße 103 | 2019-11-14 | 2019-11-17 | 2019 | 1 | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Novosibirsk, Bol'shevistskaya Ulitsa, 45 | 1987-11- | -- | 1987 | 1 | |
| Odyssée, L' | L'Odyssée | France, Périgueux, Esplanade Robert Badinter | 2017-01-12 | 2017-01-13 | 2017 | 1 | |
| Ontmoetingscentrum Aalbeke | Ontmoetingscentrum Aalbeke | Belgium, Aalbeke, Aalbekeplaats | 2001-03-12 | 2001-03-12 | 2001 | 1 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States of America, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| Ovågen | Ovågen | Norway, Øygarden | 2005-09-04 | -- | 2005 | 1 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| ONYX - Théâtre de Saint-Herblain | ONYX - Théâtre de Saint-Herblain | France, Saint-Herblain, 1 Place Océane | 2014-01-31 | -- | 2014 | 1 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Opéra-Théâtre de Limoges | Opéra-Théâtre de Limoges | France, Limoges, 48 rue Jean Jaurès | 2017-05-09 | 2017-05-11 | 2017 | 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 | |
| Oerlenbach | Oerlenbach | Germany, Oerlenbach | 2009-12-19 | -- | 2009 | 1 | |
| Örkény István Színház | Örkény István Színház | Hungary, Budapest, Madách Imre tér 6 | 2012-03-17 | -- | 2012 | 1 | |
| Ophelia Theater | Ophelia Theater | United States of America, Astoria, 21-12 30th Road | 2016-10-28 | 2016-11-13 | 2016 | 1 | |
| Opera House | Opera House | United States of America, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| Oslo Rådhus | Oslo Rådhus | Norway, Oslo, Rådhusplassen 1 | 2009-03-28 | -- | 2009 | 1 | |
| Olympia Theatre | Olympia Theatre | Ireland, Dublin, 72 Dame St | 1954-07-05 | -- | 1954 | 1 | |
| Officina Giovani - Cantieri Culturali Ex Macelli | Officina Giovani - Cantieri Culturali Ex Macelli | Italy, Prato, Piazza Macelli, 4 | 2007-04-21 | -- | 2007 | 1 | |
| Omaha | Omaha | United States of America, Omaha | 1903-11-05 | 1903-11-05 | 1903 | 1 | |
| Ostseebad Göhren | Ostseebad Göhren | Germany, Göhren | 2010-05-04 | -- | 2010 | 1 | |
| Oblastnoi dramatičeskij teatr | Oblastnoi dramatičeskij teatr | Russia, Veliky Novgorod | 1948-09- | -- | 1948 | 1 | |
| Open Scene Orlando (Instagram) | Open Scene Orlando (Instagram) | United States of America, Orlando | 2020-05-07 | 2020-06-10 | 2020 | 1 | |
| Old Auditorium, Worcester State College | Old Auditorium, Worcester State College | United States of America, Worcester, 486 Chandler Street | 1971-04-29 | 1971-05-01 | 1971 | 1 | |
| Old Red Lion Theatre | Old Red Lion Theatre | England, London, 418 St John Street | 2000-10-17 | 2000-11-11 | 2000 | 1 | |
| Ontmoetingscentrum 't Waaigat | Ontmoetingscentrum 't Waaigat | Belgium, Zwijndrecht, Kerkplein 1 | 2003-05-06 | 2003-05-06 | 2003 | 1 | |
| Orpheum Theatre | Orpheum Theatre | United States of America, Salt Lake City | 1908-06-13 | 1908-06-13 | 1908 | 1 | |
| Opéra national du Rhin | Opéra national du Rhin | France, Strasbourg, 19 place Broglie | 2020-09-19 | 2020-09-20 | 2020 | 1 | |
| Old Courthouse | Old Courthouse | Northern Ireland, Antrim, Market Square | 2011-05-26 | -- | 2011 | 1 | |
| Obfelden | Obfelden | Switzerland | 2002-04-21 | -- | 2002 | 1 | |
| Old Town Players | Old Town Players | United States of America, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
| Odda yrkesskule | Odda yrkesskule | Norway, Odda | 1970-01-23 | -- | 1970 | 1 | |
| Opera House | Opera House | United States of America, Hopkinsville | 1904-11-23 | 1904-11-23 | 1904 | 1 | |
| Ōsakafu Tachi josei sōgō sentā | Ōsakafu Tachi josei sōgō sentā (Osaka Prefectural Women's Center) | Japan, 1 Chome-3-49 Otemae, Chuo Ward, Osaka, 540-0008 | 2006-11-10 | -- | 2006 | 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 | |
| Obshtinski teatar Vazrazhdane | Obshtinski teatar Vazrazhdane | Bulgaria, Sofia, Sq. Petko Slaveykov 4 (пл. Петко Р. Славейков 4) | 1996-11-30 | -- | 1996 | 1 | |
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