| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Čeljabinsk | 1980-09- | -- | 1980 | 1 | |
| 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 | |
| Örebro | Örebro (Oerebro) | Sweden, Örebro | 1936-09-27 | -- | 1936–1970 | 3 | |
| Oliver Theatre | Oliver Theatre | United States, Lincoln | 1903-05-09 | 1908-11-03 | 1903–1908 | 2 | |
| Örnsköldsvik | Örnsköldsvik | Sweden, Örnsköldsvik | 1989-10-02 | 1989-10-02 | 1989–1993 | 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 | |
| Oriental Vevey | Oriental Vevey | Switzerland, Vevey, Rue d'Italie, 22 | 2018-10-31 | 2018-11-18 | 2018 | 2 | |
| 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 | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Ostend-Theater | Ostend-Theater | Germany, Berlin | 1878-02-06 | -- | 1878–1891 | 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 | |
| Oslo Nye Teater (Centralteatret) | Oslo Nye Teater (Centralteatret) | Norway, Oslo, Akersgata 38 | 1972-09-28 | 2017-06-17 | 1972–2017 | 10 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Oxford Playhouse | Oxford Playhouse | England, Oxford, 11-12 Beaumont Street | 1924-05-05 | 2018-02-24 | 1924–2018 | 21 | |
| Opera House | Opera House | United States, Bemidji | 1904-09-20 | 1904-09-20 | 1904 | 1 | |
| Oslo Public Library | Oslo Public Library | Norway, Oslo, Arne Garborgs plass 4 | 1988-06-30 | -- | 1988 | 1 | |
| Opernhaus Chemnitz | Opernhaus Chemnitz | Germany, Chemnitz, Theaterstraße 2 | 1927-09-27 | -- | 1927–1991 | 4 | |
| Old Auditorium, Worcester State College | Old Auditorium, Worcester State College | United States, Worcester, 486 Chandler Street | 1971-04-29 | 1971-05-01 | 1971 | 1 | |
| Opera House | Opera House | United States, Santa Cruz | 1905-07-28 | 1905-07-28 | 1905 | 1 | |
| Orosháza | Orosháza | Hungary, Orosháza | 1890-05-12 | -- | 1890–1926 | 6 | |
| Otta kulturhus | Otta kulturhus | Norway, Otta, Skansen 9 | 1993-03-07 | 2018-09-08 | 1993–2018 | 13 | |
| Orpheum | Orpheum | United States, El Paso | 1908-06-18 | 1908-06-18 | 1908 | 1 | |
| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Odensbacken | Odensbacken | Sweden | 2002-09-12 | -- | 2002 | 1 | |
| Origosenteret | Origosenteret | Norway, Svinndal, Tyritoppen 19 | 2012-11-26 | -- | 2012 | 2 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Russia, Omsk, ul. Krasnyy Put' 153 | 2005-10-01 | -- | 2005 | 1 | |
| Old Tote Theatre, The | The Old Tote Theatre | Australia, Kensington, High Street | 1967-09-23 | 1971-08-03 | 1967–1971 | 2 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
| Otta | Otta | Norway, Otta | 1971-03-19 | -- | 1971–2004 | 4 | |
| Odd Duck Studio | Odd Duck Studio | United States, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| Orăștie | Orăștie | Romania, Orăștie | 1911-02-16 | -- | 1911 | 1 | |
| Oscarsborg Festning | Oscarsborg Festning | Norway, Oscarsborg, Husvikveien | 2006-07-27 | 2007-06-24 | 2006–2007 | 2 | |
| Orlovskii dramatičeskii teatr imeni I. Turgeneva | Orlovskii dramatičeskii teatr imeni I. Turgeneva | Russia, Orel, Orel | 1944-05- | -- | 1944–1964 | 2 | |
| Opernhaus, Städtische Theater Karl-Marx-Stadt | Städtische Theater Karl-Marx-Stadt (Opernhaus) | Germany, Karl-Marx-Stadt (Chemnitz), Theaterplatz | 1956-04-29 | -- | 1956 | 1 | |
| Oxfordshire | Oxfordshire | England | 2020-05-08 | -- | 2020 | 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 | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Old Town Players | Old Town Players | United States, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
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