| OC Vondel (Ontmoetingscentrum Meulebeke) | OC Vondel (Ontmoetingscentrum Meulebeke) | Belgium, Meulebeke, Karel van Manderstraat 26 | 2002-02-28 | 2002-02-28 | 2002 | 1 | |
| Oberlin College & Conservatory, Hall auditorium | Oberlin College & Conservatory | United States, Oberlin, 67 North Main St. | 2014-04-17 | 2014-04-19 | 2014 | 1 | |
| Osobnyak Theatre | Osobnyak Theatre | Russia, St. Petersburg, Kamennoostrovsky 55 | 2011-05-15 | 2011-05-17 | 2011 | 1 | |
| Old Courthouse | Old Courthouse | Northern Ireland, Antrim, Market Square | 2011-05-26 | -- | 2011 | 1 | |
| Odda yrkesskule | Odda yrkesskule | Norway, Odda | 1970-01-23 | -- | 1970 | 1 | |
| Ohio State University | Ohio State University | United States, Columbus, 1739 North High Street | 1981-02-27 | 2001-03-04 | 1981–2001 | 2 | |
| Oddemarka skole | Oddemarka skole | Norway, Kristiansand, Kristiansand | 2006-11-08 | -- | 2006 | 1 | |
| Olathe Opera House | Olathe Opera House | United States, Olathe | 1908-01-31 | 1908-01-31 | 1908 | 1 | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Oseana Kunst & Kultursenter | Oseana Kunst & Kultursenter | Norway, Os, Mobergsbakken 20 | 2012-09-18 | 2020-09-13 | 2012–2020 | 5 | |
| Olympic Theatre | Olympic Theatre | United States, St. Louis | 1891-01-11 | 1910-04-03 | 1891–1910 | 7 | |
| Oradea | Oradea | Romania, Oradea | 1890-08-02 | 1936-08-25 | 1890–2012 | 13 | |
| Off Latina | Off Latina | Spain, Madrid, Calle de los Mancebos, 4 | 2019-11-07 | 2020-04-29 | 2019 | 1 | |
| Odeïon | Odeïon | Austria, Salzburg/Langwied, Waldorfstraße 13 | 2013-09-26 | 2013-10-27 | 2013 | 1 | |
| Opernhaus Graz | Opernhaus Graz | Austria, Graz, Opernring | 1912-05-24 | -- | 1912 | 2 | |
| Onafhankelijk Toneel | Onafhankelijk Toneel | Netherlands, Rotterdam, Sint-Jobsweg 3 | 1998-05-21 | 2009-11-22 | 1998–2009 | 4 | |
| Ohkuma Auditorium | Ohkuma Auditorium | Japan, Tokyo, Japan | 1954-09-11 | -- | 1954–1965 | 3 | |
| Opera House | Opera House | United States, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Other Place, The | The Other Place | England, Stratford-upon-Avon, Warwickshire, Waterside | 1981-07-06 | 1982-07-30 | 1981–1996 | 4 | |
| Oskar-Herbig-Halle | Oskar-Herbig-Halle | Germany, Mellrichstadt, Bahnhofstr. 17 | 2004-03-03 | -- | 2004–2011 | 2 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| O'Connell Theatre | O'Connell Theatre | United States, Dekalb, Stevens Building, School of Theatre and Dance Northern Illinois University | 2009-02-19 | 2009-03-01 | 2009 | 1 | |
| Obshtinski teatar Vazrazhdane | Obshtinski teatar Vazrazhdane | Bulgaria, Sofia, Sq. Petko Slaveykov 4 (пл. Петко Р. Славейков 4) | 1996-11-30 | -- | 1996 | 1 | |
| Obldramteatr | Obldramteatr | Russia, Ivanovo | 1940-03-24 | -- | 1940 | 1 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| Ódry Színpad | Ódry Színpad | Hungary, Budapest, Vas utca 2 | 1967-12-16 | -- | 1967–2017 | 3 | |
| OC De Buiting | OC De Buiting (Cultuur, gemeenschaps of ontmoetingscentrum) | Belgium, Beringen, Tessenderlosesteenweg 18 | 2007-11-29 | 2007-11-30 | 2007 | 1 | |
| Ovågen | Ovågen | Norway, Øygarden | 2005-09-04 | -- | 2005 | 1 | |
| Odense Theater | Odense Theater | Denmark, Odense, Sortebrødre Torv | 1876-04-20 | 1899-10-20 | 1876–1901 | 9 | |
| Opéra de Dijon | Opéra de Dijon | France, Dijon, 11 Boulevard de Verdun | 2014-03-10 | 2014-03-12 | 2014 | 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 | |
| Örnsköldsvik | Örnsköldsvik | Sweden, Örnsköldsvik | 1989-10-02 | 1989-10-02 | 1989–1993 | 2 | |
| Odeon de Spiegel | Odeon de Spiegel | Netherlands, Zwolle, Blijmarkt 25 | 2000-04-28 | -- | 2000–2008 | 2 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Open Space Theatre | Open Space Theatre | United States, New York | 1982-01-11 | -- | 1982 | 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 | |
| Oerol Festival | Oerol Festival | Netherlands, Terschelling | 2014-06-13 | 2016-06-18 | 2014–2016 | 2 | |
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