| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Odense Folketeater | Odense Folketeater | Denmark, Odense | 1907-10-29 | 1907-11-15 | 1907–1908 | 7 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Opernhaus Chemnitz | Opernhaus Chemnitz | Germany, Chemnitz, Theaterstraße 2 | 1927-09-27 | -- | 1927–1991 | 4 | |
| Odensbacken | Odensbacken | Sweden | 2002-09-12 | -- | 2002 | 1 | |
| Opera House | Opera House | United States of America, Pensacola | 1903-10-25 | 1903-10-25 | 1903 | 1 | |
| Oscarsborg Festning | Oscarsborg Festning | Norway, Oscarsborg, Husvikveien | 2006-07-27 | 2007-06-24 | 2006–2007 | 2 | |
| Opera House | Opera House | United States of America, Santa Cruz | 1905-07-28 | 1905-07-28 | 1905 | 1 | |
| Oblastnoi dramteatr Volgograd | Oblastnoi dramteatr Volgograd | Russia, Volgograd | 1948-10- | -- | 1948 | 1 | |
| Oppdal Kulturhus | Oppdal Kulturhus | Norway, Oppdal, Inge Krokanns veg 2 | 2009-11-12 | 2015-10-08 | 2009–2017 | 5 | |
| Odd Duck Studio | Odd Duck Studio | United States of America, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Oradea | Oradea | Romania, Oradea | 1890-08-02 | 1936-08-25 | 1890–2012 | 13 | |
| Old Auditorium, Worcester State College | Old Auditorium, Worcester State College | United States of America, Worcester, 486 Chandler Street | 1971-04-29 | 1971-05-01 | 1971 | 1 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Otta kulturhus | Otta kulturhus | Norway, Otta, Skansen 9 | 1993-03-07 | 2018-09-08 | 1993–2022 | 14 | |
| Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Russia, Omsk, ul. Krasnyy Put' 153 | 2005-10-01 | -- | 2005 | 1 | |
| Ontmoetingscentrum Aalbeke | Ontmoetingscentrum Aalbeke | Belgium, Aalbeke, Aalbekeplaats | 2001-03-12 | 2001-03-12 | 2001 | 1 | |
| Onde, L' | L'Onde | France, Vélizy-Villacoublay, 8 bis Avenue Louis Breguet | 2015-05-19 | 2018-01-19 | 2015–2018 | 2 | |
| Odda kino | Odda kino | Norway, Odda, Opheimsgata 31, 5750 ODDA | 1969-09-26 | -- | 1969–1978 | 4 | |
| Opernhaus, Städtische Theater Karl-Marx-Stadt | Städtische Theater Karl-Marx-Stadt (Opernhaus) | Germany, Karl-Marx-Stadt (Chemnitz), Theaterplatz | 1956-04-29 | -- | 1956 | 1 | |
| Obshtinski teatar Vazrazhdane | Obshtinski teatar Vazrazhdane | Bulgaria, Sofia, Sq. Petko Slaveykov 4 (пл. Петко Р. Славейков 4) | 1996-11-30 | -- | 1996 | 1 | |
| Otta | Otta | Norway, Otta | 1971-03-19 | -- | 1971–2004 | 4 | |
| Opernhaus Graz | Opernhaus Graz | Austria, Graz, Opernring | 1912-05-24 | -- | 1912 | 2 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Opéra National de Lyon | Opéra National de Lyon | France, Lyon, 1 place de la Comédie | 2022-06-04 | 2022-06-13 | 2022 | 1 | |
| Örebro | Örebro | Sweden, Örebro | 1936-09-27 | -- | 1936–1970 | 3 | |
| Odyssée, L' | L'Odyssée | France, Périgueux, Esplanade Robert Badinter | 2017-01-12 | 2017-01-13 | 2017 | 1 | |
| Old Town Players | Old Town Players | United States of America, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
| Orpheum | Orpheum | Germany, Munich | 1893-03-08 | -- | 1893–1895 | 3 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Observatoriet | Observatoriet | Norway, Oslo, Observatoriegata 1 | 2007-06-12 | 2007-08-17 | 2007–2013 | 2 | |
| Opera House | Opera House | United States of America, Telluride | -- | -- | | | |
| Oden Hall | Oden Hall | United States of America, Dr, Gambier, 107 College | 2024-04-07 | 2024-04-07 | 2024 | 1 | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Onafhankelijk Toneel | Onafhankelijk Toneel | Netherlands, Rotterdam, Sint-Jobsweg 3 | 1998-05-21 | 2009-11-22 | 1998–2009 | 4 | |
| Opera House | Opera House | United States of America, Detroit | 1896-02-18 | 1910-09-28 | 1896–1910 | 2 | |
| Opera House | Opera House | United States of America, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| Oberammergau, Passionstheater | Passionstheater Oberammergau | Germany, Oberammergau, Othmar-Weis-Str. | 2016-07-01 | 2016-07-23 | 2016 | 1 | |
| Open Space Theatre | Open Space Theatre | United States of America, New York | 1982-01-11 | -- | 1982 | 1 | |
| Ōsaka Chikamatsu-za | Ōsaka Chikamatsu-za (Chikamatsuza Theatre) | Japan, Osaka | 1913-11-21 | 1913-11-25 | 1913 | 1 | |
| Opéra-Théâtre de Limoges | Opéra-Théâtre de Limoges | France, Limoges, 48 rue Jean Jaurès | 2017-05-09 | 2017-05-11 | 2017 | 1 | |
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