| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Olathe Opera House | Olathe Opera House | United States, Olathe | 1908-01-31 | 1908-01-31 | 1908 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Odder Theater | Odder Theater | Denmark, Odder | 1905-11-25 | -- | 1905 - 1907 | 4 | |
| Octagon, The | The Octagon | United States, Montgomery, 1 Festival Drive | 1997-03-04 | 2002-04-14 | 1997 - 2002 | 2 | |
| Oerol Festival | Oerol Festival | Netherlands, Terschelling | 2014-06-13 | 2016-06-18 | 2014 - 2016 | 2 | |
| Oda Tiyatrosu | Atatürk Kültür Merkezi Oda Tiyatrosu (AKM Oda Tiyatrosu) | Turkey, Istanbul, Gümüşsuyu Mahallesi, Tak-ı Zafer Cd., Beyoğlu | 1975-- | 1976-- | 1975 | 1 | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Opera House | Opera House | United States, New Ulm | 1905-01-15 | 1905-01-15 | 1905 | 1 | |
| 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 | |
| Olivier Theatre | Olivier Theatre | England, Southbank, London, National Theatre, Upper Ground | 1978-04-25 | 2019-10-08 | 1978 - 2019 | 11 | |
| Orkanger | Orkanger | Norway, Orkanger | 1958-01-23 | -- | 1958 - 2005 | 5 | |
| Odsherred Teater | Odsherred Teater | Denmark, Nykobing Sjaelland, Annebergparken 22 | 2002-02-27 | -- | 2002 - 2006 | 2 | |
| Oravița | Oravița | Romania, Oravița | 1884-12-08 | 1884-12-23 | 1884 - 1913 | 3 | |
| Odeïon | Odeïon | Austria, Salzburg/Langwied, Waldorfstraße 13 | 2013-09-26 | 2013-10-27 | 2013 | 1 | |
| Opera House | Opera House | United States, Logan | 1905-04-15 | 1905-04-15 | 1905 | 1 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Oslo Konserthus | Oslo Konserthus | Norway, Oslo, Munkedamsveien 14 | 2004-05-26 | 2008-04-18 | 2004 - 2008 | 2 | |
| OC Westrand | OC Westrand | Belgium, Dilbeek, Kamerijklaan z/n | 1994-04-14 | -- | 1994 - 2004 | 4 | |
| Opera House | Opera House | New Zealand, Wellington, 111/113 Manners Street | 1890-11-28 | 1890-11-29 | 1890 | 1 | |
| Oliver Theatre | Oliver Theatre | United States, Lincoln | 1903-05-09 | 1908-11-03 | 1903 - 1908 | 2 | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Obfelden | Obfelden | Switzerland | 2002-04-21 | -- | 2002 | 1 | |
| Old Town Hall Arts Center | Old Town Hall Arts Center | England, Hertfordshire, Hemel Hempstead | 1985-02-18 | 1985-02-20 | 1985 - 2011 | 2 | |
| Olavskapellet, Borgarsyssel Museum | Olavskapellet, Borgarsyssel Museum | Norway, Sarpsborg, Gamlebygaten 8 | 2006-08-01 | 2006-08-02 | 2006 | 1 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | -- | -- | | | |
| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Orkanger | 2012-11-11 | 2015-10-09 | 2012 - 2015 | 4 | |
| 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 | |
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Venues
