| Opština Bečej | Opština Bečej | Serbia, Opština Bečej | 1903-03-11 | -- | 1903 | 1 | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Öteki Tiyatro | Öteki Tiyatro | Turkey, Maltepe/ANKARA, Gazi Mustafa Kemal Bulvarı No:114-C | 2007-06-23 | -- | 2007 | 1 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Odenkirchen | Odenkirchen | Germany, Odenkirchen | 1893-10-07 | -- | 1893 | 1 | |
| Otta Samfunnshus | Otta Samfunnshus | Norway, Otta, Klyphaugvegen 8, 2670 Otta | 1973-09-30 | -- | 1973–1987 | 4 | |
| Ovalhouse | Ovalhouse | England, London, 52-54 Kennington Oval | 2018-05-17 | 2018-05-19 | 2018 | 1 | |
| Oerlenbach | Oerlenbach | Germany, Oerlenbach | 2009-12-19 | -- | 2009 | 1 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Oslo Nye Trikkestallen | Oslo Nye Trikkestallen | Norway, Oslo, Torshovgata 33 | 2011-07-01 | 2019-01-06 | 2011–2019 | 2 | |
| Obergrafschaft, Theater der | Theater der Obergrafschaft | Germany, Schüttorf, Hermann-Schlikker-Str. 1-3 | 2015-10-03 | -- | 2015 | 1 | |
| Opera House | Opera House | United States, Telluride | -- | -- | | | |
| Opernhaus Unter den Linden | Opernhaus Unter den Linden | Germany, Berlin | 1905-09-20 | -- | 1905 | 1 | |
| Owl Spot | Owl Spot | Japan, Tokyo | 2009-02-04 | 2016-11-23 | 2009–2016 | 7 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 1 | |
| Opera House | Opera House | United States, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Oblasni dram teatr | Oblasni dram teatr | Russia, Kaliningrad, Prospekt Mira, 4 | 1960-01- | -- | 1960–1973 | 2 | |
| Odense Teater | Odense Teater | Denmark, Odense, Jernbanegade 21 | 1928-04-30 | 2018-10-13 | 1928–2018 | 16 | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Örkény István Színház | Örkény István Színház | Hungary, Budapest, Madách Imre tér 6 | 2012-03-17 | -- | 2012 | 1 | |
| OBOS-gården Wesselsgate 15 | OBOS-gården Wesselsgate 15 | Norway, Oslo, Museumsveien 10 | 2006-05-20 | 2008-06-13 | 2006–2008 | 2 | |
| 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 | |
| Odder Theater | Odder Theater | Denmark, Odder | 1905-11-25 | -- | 1905–1907 | 4 | |
| Old Vic, The | The Old Vic | England, London, The Cut | 1922-03-06 | 2016-03-19 | 1922–2016 | 11 | |
| Oliver Theatre | Oliver Theatre | United States, Lincoln | 1903-05-09 | 1908-11-03 | 1903–1908 | 2 | |
| Ostseebad Göhren | Ostseebad Göhren | Germany, Göhren | 2010-05-04 | -- | 2010 | 1 | |
| Ohnsorg Theater | Ohnsorg Theater | Germany, Hamburg, Heidi-Kabel-Platz 1 | 1995-04-24 | 2002-05-25 | 1995–2002 | 2 | |
| Opera House | Opera House | New Zealand, Wellington, 111/113 Manners Street | 1890-11-28 | 1890-11-29 | 1890 | 1 | |
| Opera House | Opera House | United States, Kentucky, Kentucky | 1899-12-20 | 1903-12-10 | 1899–1903 | 2 | |
| Ontmoetingscentrum 't Waaigat | Ontmoetingscentrum 't Waaigat | Belgium, Zwijndrecht, Kerkplein 1 | 2003-05-06 | 2003-05-06 | 2003 | 1 | |
| Oslo Konserthus | Oslo Konserthus | Norway, Oslo, Munkedamsveien 14 | 2004-05-26 | 2008-04-18 | 2004–2008 | 2 | |
| Olofström | Olofström | Sweden, Olofström | 1992-11-12 | -- | 1992 | 1 | |
| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Osobnyak Theatre | Osobnyak Theatre | Russia, St. Petersburg, Kamennoostrovsky 55 | 2011-05-15 | 2011-05-17 | 2011 | 1 | |
| Opole | Opole | Poland, Opole | -- | -- | | | |
| Oslo | Oslo | Norway, Oslo | 1926-09- | 2008-10-02 | 1926–2014 | 11 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Orpheum Theatre | Orpheum Theatre | United States, Salt Lake City | 1908-06-13 | 1908-06-13 | 1908 | 1 | |
| Oberlin College & Conservatory, Hall auditorium | Oberlin College & Conservatory | United States, Oberlin, 67 North Main St. | 2014-04-17 | 2014-04-19 | 2014 | 1 | |
| Odeon Theatre | Odeon Theatre | United States, St. Louis | 1905-10-04 | 1912-03-27 | 1905–1912 | 2 | |
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