| Opera House | Opera House | United States | 1899-12-20 | 1899-12-20 | 1899 | 1 | |
| Ostersund | Ostersund | Sweden, Ostersund | 1936-10-30 | -- | 1936 | 1 | |
| Ornans | Ornans | France, Ornans | 2001-- | -- | 2001 | 1 | |
| Otta Samfunnshus | Otta Samfunnshus | Norway, Otta, Klyphaugvegen 8, 2670 Otta | 1973-09-30 | -- | 1973 - 1987 | 4 | |
| Oslo Nye Teater (Centralteatret) | Oslo Nye Teater (Centralteatret) | Norway, Oslo, Akersgata 38 | 1972-09-28 | 2017-06-17 | 1972 - 2017 | 10 | |
| Odense | Odense | Denmark, Odense | 1948-04-20 | -- | 1948 - 2000 | 2 | |
| Osobnyak Theatre | Osobnyak Theatre | Russia, St. Petersburg, Kamennoostrovsky 55 | 2011-05-15 | 2011-05-17 | 2011 | 1 | |
| Ottawa Little Theatre Group | Ottawa Little Theatre Group | Canada, Ottawa | 1945-12-20 | -- | 1945 | 1 | |
| Opera House | Opera House | United States, Santa Cruz | 1905-07-28 | 1905-07-28 | 1905 | 1 | |
| Odda ungdomsskole | Odda ungdomsskole | Norway, Odda, Eidesmoen | 2006-11-15 | -- | 2006 | 1 | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Operahuset Nordfjord | Operahuset Nordfjord | Norway, Nordfjord, Sophus Lie-vegen 3 | 2009-11-09 | -- | 2009 - 2017 | 6 | |
| Oslo | Oslo | Norway, Oslo | 1928-02-28 | 2008-10-02 | 1928 - 2014 | 9 | |
| Ohio State University | Ohio State University | United States, Columbus, 1739 North High Street | 1981-02-27 | 2001-03-04 | 1981 - 2001 | 2 | |
| Oscarshall | Oscarshall | Norway, Oslo, Oscarshallveien | 2017-08-28 | 2017-11-28 | 2017 | 1 | |
| Opera House | Opera House | United States, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| OPERATTEN im STATTtheater | OPERATTEN im STATTtheater | Switzerland, Stäfa, Bahnhofstrasse 52 | 2007-03-07 | 2007-04-21 | 2007 | 1 | |
| Open Space Theatre | Open Space Theatre | United States, New York | 1982-01-11 | -- | 1982 | 1 | |
| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Orkanger | 2012-11-11 | 2015-10-09 | 2012 - 2015 | 4 | |
| Old Vic, The | The Old Vic | England, London, The Cut | 1922-03-06 | 2016-03-19 | 1922 - 2016 | 11 | |
| Opera Comique Theatre | Opera Comique Theatre | England, London | 1889-07-17 | 1895-03-30 | 1889 - 1895 | 6 | |
| Opera Națională București | Opera Națională București | Romania, Bucharest, Bulevardul Mihail Kogălniceanu 70-72 | 2007-05-09 | -- | 2007 | 1 | |
| Overholser Theatre | Overholser Theatre | United States, Ardmore | 1910-12-21 | 1910-12-21 | 1910 | 1 | |
| OC De Buiting | OC De Buiting (Cultuur, gemeenschaps of ontmoetingscentrum) | Belgium, Beringen, Tessenderlosesteenweg 18 | 2007-11-29 | 2007-11-30 | 2007 | 1 | |
| Orange Tree Theatre, The | The Orange Tree Theatre | England, London, 1 Clarence St, Richmond | 1991-10-10 | 2012-12-15 | 1991 - 2012 | 3 | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| Opera House | Opera House | United States, Pensacola | 1903-10-25 | 1903-10-25 | 1903 | 1 | |
| Orkdal Samfunnshus | Orkdal Samfunnshus | Norway, Fannrem | 1978-11-22 | -- | 1978 | 1 | |
| Opera House | Opera House | United States, New Castle | 1907-03-09 | 1907-03-09 | 1907 | 1 | |
| Ontmoetingscentrum d'Iefte | Ontmoetingscentrum d'Iefte | Belgium, Deerlijk, Hoogstraat 122 | 2002-01-14 | 2002-01-15 | 2002 | 1 | |
| Orosháza | Orosháza | Hungary, Orosháza | 1890-05-12 | -- | 1890 - 1926 | 6 | |
| Oravais Teater | Oravais Teater | Finland, Kimo, Oravais, Kyroboas Kvarn | 1996-07-11 | -- | 1996 | 1 | |
| Oskarshamn | Oskarshamn | Sweden, Oskarshamn | 1991-05-03 | 1991-05-03 | 1991 - 1992 | 2 | |
| Opernhaus Chemnitz | Opernhaus Chemnitz | Germany, Chemnitz, Theaterstraße 2 | 1927-09-27 | -- | 1927 - 1991 | 4 | |
| Onafhankelijk Toneel | Onafhankelijk Toneel | Netherlands, Rotterdam, Sint-Jobsweg 3 | 1998-05-21 | 2009-11-22 | 1998 - 2009 | 4 | |
| Obergrafschaft, Theater der | Theater der Obergrafschaft | Germany, Schüttorf, Hermann-Schlikker-Str. 1-3 | 2015-10-03 | -- | 2015 | 1 | |
| Oranjerie | Oranjerie | Netherlands, Roermond, Kloosterwandplein 12-16 | 2009-11-07 | -- | 2009 | 1 | |
| Opern- und Schauspielhaus Hannover | Opern- und Schauspielhaus Hannover | Germany, Hannover | 1920-06-21 | -- | 1920 - 1924 | 2 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Opština Bečej | Opština Bečej | Serbia, Opština Bečej | 1903-03-11 | -- | 1903 | 1 | |
| Odeon | Odeon | Argentina, Buenos Aires | 1904-06-24 | 1904-06-26 | 1904 | 1 | |
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Venues
