| Otta | Otta | Norway, Otta | 1971-03-19 | -- | 1971–2004 | 4 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Oscarsborg Festning | Oscarsborg Festning | Norway, Oscarsborg, Husvikveien | 2006-07-27 | 2007-06-24 | 2006–2007 | 2 | |
| 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 | |
| Obfelden | Obfelden | Switzerland | 2002-04-21 | -- | 2002 | 1 | |
| Odda yrkesskule | Odda yrkesskule | Norway, Odda | 1970-01-23 | -- | 1970 | 1 | |
| Odeon Theatre | Odeon Theatre | United States, St. Louis | 1905-10-04 | 1912-03-27 | 1905–1912 | 2 | |
| Oslo fengsel | Oslo fengsel | Norway, Oslo, Åkebergveien 11 | 2012-11-27 | -- | 2012 | 2 | |
| Overholser Theatre | Overholser Theatre | United States, Ardmore | 1910-12-21 | 1910-12-21 | 1910 | 1 | |
| Oskarshamn | Oskarshamn | Sweden, Oskarshamn | 1991-05-03 | 1991-05-03 | 1991–1992 | 2 | |
| Old Town Players | Old Town Players | United States, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| 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 | |
| Odda ungdomsskole | Odda ungdomsskole | Norway, Odda, Eidesmoen | 2006-11-15 | -- | 2006 | 1 | |
| Opernhaus Graz | Opernhaus Graz | Austria, Graz, Opernring | 1912-05-24 | -- | 1912 | 2 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| OC De Neerbeek | OC De Neerbeek (Ontmoetingscentrum De Neerbeek) | Belgium, Bissegem, Vlaswaagplein 1 | 2002-01-10 | 2002-01-10 | 2002–2007 | 2 | |
| Opera House | Opera House | United States, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Otto-Klenert-Schule | Otto-Klenert-Schule | Germany, Bad Friedrichshall, Rathausplatz 7 | 2006-02-18 | -- | 2006 | 1 | |
| Oulun Kaupunginteatteri | Oulun Kaupunginteatteri | Finland, Oulu, Kaarlenväylä 2 | 1963-- | 1972-04-27 | 1963–1985 | 3 | |
| Orpheum | Orpheum | Germany, Munich | 1893-03-08 | -- | 1893–1895 | 3 | |
| 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 | |
| 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 | |
| Olavskapellet, Borgarsyssel Museum | Olavskapellet, Borgarsyssel Museum | Norway, Sarpsborg, Gamlebygaten 8 | 2006-08-01 | 2006-08-02 | 2006 | 1 | |
| Octagon, The | The Octagon | United States, Montgomery, 1 Festival Drive | 1997-03-04 | 2002-04-14 | 1997–2002 | 2 | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Odeon | Odeon | Argentina, Buenos Aires | 1904-06-24 | 1904-06-26 | 1904 | 1 | |
| Orange Tree Theatre, The | The Orange Tree Theatre | England, London, 1 Clarence St, Richmond | 1991-10-10 | 2012-12-15 | 1991–2012 | 3 | |
| Olavshallen | Olavshallen | Norway, Trondheim, Kjøpmannsgata 44 | 1997-05-15 | 2008-02-29 | 1997–2008 | 5 | |
| Överkalix Folkets Hus | Överkalix Folkets Hus | Sweden, Överkalix, Bulandsgatan 2 | 2010-11-16 | -- | 2010 | 1 | |
| Odeon-Theater | Odeon-Theater | Germany, Goslar, Bismarckstraße 1 | 1997-10-10 | 1997-10-10 | 1997–2005 | 2 | |
| 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 | |
| Oppdal Kulturhus | Oppdal Kulturhus | Norway, Oppdal, Inge Krokanns veg 2 | 2009-11-12 | 2015-10-08 | 2009–2017 | 5 | |
| Old American Can Factory, The | The Old American Can Factory | United States, Brooklyn, 232 3rd Street | 2003-03-06 | 2003-06-07 | 2003 | 2 | |
| Odda kino | Odda kino | Norway, Odda, Opheimsgata 31, 5750 ODDA | 1969-09-26 | -- | 1969–1978 | 4 | |
| Odda | Odda | Norway, Odda | 1951-04-25 | 1958-03-02 | 1951–1982 | 6 | |
| Old globe theatre, the | The Old Globe Theatre | United States, San Diego, 1363 Old Globe Way | 1995-04-30 | 1995-06-18 | 1995 | 1 | |
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