| Oberammergau, Passionstheater | Passionstheater Oberammergau | Germany, Oberammergau, Othmar-Weis-Str. | 2016-07-01 | 2016-07-23 | 2016 | 1 | |
| Óbudai Kisfaludy Színház | Óbudai Kisfaludy Színház | Hungary, Budapest | 1900-04-15 | -- | 1900 | 1 | |
| Obergrafschaft, Theater der | Theater der Obergrafschaft | Germany, Schüttorf, Hermann-Schlikker-Str. 1-3 | 2015-10-03 | -- | 2015 | 1 | |
| Opera House | Opera House | United States, Logan | 1905-04-15 | 1905-04-15 | 1905 | 1 | |
| Opéra Orchestre national Montpellier Occitanie | Opéra Orchestre national Montpellier Occitanie | France, Montpellier, 11 Boulevard Victor Hugo | 2018-01-12 | 2018-01-13 | 2018 | 1 | |
| Oulun Kaupunginteatteri | Oulun Kaupunginteatteri | Finland, Oulu, Kaarlenväylä 2 | 1963-- | 1972-04-27 | 1963–1985 | 3 | |
| Otta | Otta | Norway, Otta | 1971-03-19 | -- | 1971–2004 | 4 | |
| Oscarsborg Festning | Oscarsborg Festning | Norway, Oscarsborg, Husvikveien | 2006-07-27 | 2007-06-24 | 2006–2007 | 2 | |
| Old Town Players | Old Town Players | United States, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
| Old Rep at Birmingham Repertory Theatre | The Old Rep at Birmingham Repertory Theatre | England, Birmingham | 2013-03-14 | 2013-03-28 | 2013 | 1 | |
| Old Fire Station Studio Theatre | Old Fire Station Studio Theatre | England, Oxford, 40 George St | 2003-11-11 | 2018-10-06 | 2003–2018 | 2 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 1 | |
| Opera House | Opera House | United States, New Castle | 1904-04-29 | 1908-04-11 | 1904–1908 | 2 | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Olavskapellet, Borgarsyssel Museum | Olavskapellet, Borgarsyssel Museum | Norway, Sarpsborg, Gamlebygaten 8 | 2006-08-01 | 2006-08-02 | 2006 | 1 | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Oppdal Kulturhus | Oppdal Kulturhus | Norway, Oppdal, Inge Krokanns veg 2 | 2009-11-12 | 2015-10-08 | 2009–2017 | 5 | |
| Otto-Klenert-Schule | Otto-Klenert-Schule | Germany, Bad Friedrichshall, Rathausplatz 7 | 2006-02-18 | -- | 2006 | 1 | |
| Orange Tree Theatre, The | The Orange Tree Theatre | England, London, 1 Clarence St, Richmond | 1991-10-10 | 2012-12-15 | 1991–2012 | 3 | |
| Orpheum | Orpheum | Germany, Munich | 1893-03-08 | -- | 1893–1895 | 3 | |
| Oosterpoort Groningen, De | De Oosterpoort Groningen | Netherlands, 9724 DA, Trompsingel 27, | 2000-04-20 | 2000-04-21 | 2000 | 1 | |
| Olomouc | Olomouc | Czech Republic, Olomouc | 2007-05-17 | -- | 2007 | 1 | |
| Oliver Theatre | Oliver Theatre | United States, Lincoln | 1903-05-09 | 1908-11-03 | 1903–1908 | 2 | |
| Overture Center for the Arts, The Playhouse | Overture Center for the Arts, The Playhouse | United States, Madison, 201 State St | 2010-03-18 | 2010-03-28 | 2010 | 1 | |
| Ovalhouse | Ovalhouse | England, London, 52-54 Kennington Oval | 2018-05-17 | 2018-05-19 | 2018 | 1 | |
| Oblasni dram teatr | Oblasni dram teatr | Russia, Kaliningrad, Prospekt Mira, 4 | 1960-01- | -- | 1960–1973 | 2 | |
| Odda kino | Odda kino | Norway, Odda, Opheimsgata 31, 5750 ODDA | 1969-09-26 | -- | 1969–1978 | 4 | |
| Octagon, The | The Octagon | United States, Montgomery, 1 Festival Drive | 1997-03-04 | 2002-04-14 | 1997–2002 | 2 | |
| Old globe theatre, the | The Old Globe Theatre | United States, San Diego, 1363 Old Globe Way | 1995-04-30 | 1995-06-18 | 1995 | 1 | |
| Odeon | Odeon | Argentina, Buenos Aires | 1904-06-24 | 1904-06-26 | 1904 | 1 | |
| Opera House | Opera House | United States, Kentucky, Kentucky | 1899-12-20 | 1903-12-10 | 1899–1903 | 2 | |
| Opern- und Schauspielhaus Hannover | Opern- und Schauspielhaus Hannover | Germany, Hannover | 1920-06-21 | -- | 1920–1924 | 2 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Opera House | Opera House | United States, Bemidji | 1904-09-20 | 1904-09-20 | 1904 | 1 | |
| Osses, Théâtre des | Théâtre des Osses | Switzerland, Givisiez, Place des Osses 1 | 2011-02-10 | 2011-02-27 | 2011 | 1 | |
| Örebro | Örebro (Oerebro) | Sweden, Örebro | 1936-09-27 | -- | 1936–1970 | 3 | |
| Old American Can Factory, The | The Old American Can Factory | United States, Brooklyn, 232 3rd Street | 2003-03-06 | 2003-06-07 | 2003 | 2 | |
| Olavshallen | Olavshallen | Norway, Trondheim, Kjøpmannsgata 44 | 1997-05-15 | 2008-02-29 | 1997–2008 | 5 | |
| Onassis Cultural Centre, Upper Stage | Onassis Cultural Centre, Upper Stage | Greece, Athens, 107-109 Syngrou Avenue | 2014-12-22 | 2015-01-04 | 2014–2015 | 2 | |
| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Odensbacken | Odensbacken | Sweden | 2002-09-12 | -- | 2002 | 1 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
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