| Omaha | Omaha | United States, Omaha | 1903-11-05 | 1903-11-05 | 1903 | 1 | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Opera House | Opera House | United States, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Olten | Olten | Switzerland, Olten | 2003-02-17 | -- | 2003 | 1 | |
| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Orkanger | 2012-11-11 | 2015-10-09 | 2012–2015 | 4 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Östersund | Östersund | Sweden, Östersund | 1879-- | -- | 1879 | 1 | |
| Ostersund | Ostersund | Sweden, Ostersund | 1936-10-30 | -- | 1936 | 1 | |
| Olympic Theatre | Olympic Theatre | United States, St. Louis | 1891-01-11 | 1910-04-03 | 1891–1910 | 7 | |
| Old Fire Station Studio Theatre | Old Fire Station Studio Theatre | England, Oxford, 40 George St | 2003-11-11 | 2018-10-06 | 2003–2018 | 2 | |
| Old Vic, The | The Old Vic | England, London, The Cut | 1922-03-06 | 2016-03-19 | 1922–2016 | 11 | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Opernhaus | Opernhaus | Germany, Frankfurt, Opernplatz 1 | 1892-12-10 | -- | 1892–1940 | 2 | |
| Odéon-Théâtre de l'Europe | Odéon-Théâtre de l'Europe | France, Paris, 67 Rue Monsieur le Prince | 1993-03-12 | 2019-11-21 | 1993–2019 | 5 | |
| Ottawa Little Theatre Group | Ottawa Little Theatre Group | Canada, Ottawa | 1945-12-20 | -- | 1945 | 1 | |
| Opera House | Opera House | United States, Dixon | 1904-11-30 | 1907-12-21 | 1904–1907 | 2 | |
| Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Russia, Omsk, ul. Krasnyy Put' 153 | 2005-10-01 | -- | 2005 | 1 | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Oslo Public Library | Oslo Public Library | Norway, Oslo, Arne Garborgs plass 4 | 1988-06-30 | -- | 1988 | 1 | |
| Opernhaus Unter den Linden | Opernhaus Unter den Linden | Germany, Berlin | 1905-09-20 | -- | 1905 | 1 | |
| Odense Teater | Odense Teater | Denmark, Odense, Jernbanegade 21 | 1928-04-30 | 2018-10-13 | 1928–2018 | 16 | |
| Opera House | Opera House | United States, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Oscarshall | Oscarshall | Norway, Oslo, Oscarshallveien | 2017-08-28 | 2017-11-28 | 2017 | 1 | |
| Opera House | Opera House | United States, New Castle | 1904-04-29 | 1908-04-11 | 1904–1908 | 2 | |
| Officina Giovani - Cantieri Culturali Ex Macelli | Officina Giovani - Cantieri Culturali Ex Macelli | Italy, Prato, Piazza Macelli, 4 | 2007-04-21 | -- | 2007 | 1 | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Opernhaus Hannover | Opernhaus Hannover | Germany, Hannover, Opernplatz 1 | 1928-03-06 | 1956-12-05 | 1928–1956 | 2 | |
| Odense Folketeater | Odense Folketeater | Denmark, Odense | 1907-10-29 | 1907-11-15 | 1907–1908 | 7 | |
| Other Place, The | The Other Place | England, Stratford-upon-Avon, Warwickshire, Waterside | 1981-07-06 | 1982-07-30 | 1981–1996 | 4 | |
| Observatoriet | Observatoriet | Norway, Oslo, Observatoriegata 1 | 2007-06-12 | 2007-08-17 | 2007–2013 | 2 | |
| Öteki Tiyatro | Öteki Tiyatro | Turkey, Maltepe/ANKARA, Gazi Mustafa Kemal Bulvarı No:114-C | 2007-06-23 | -- | 2007 | 1 | |
| Odd Duck Studio | Odd Duck Studio | United States, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| OC De Neerbeek | OC De Neerbeek (Ontmoetingscentrum De Neerbeek) | Belgium, Bissegem, Vlaswaagplein 1 | 2002-01-10 | 2002-01-10 | 2002–2007 | 2 | |
| Ocna Mureș | Ocna Mureș | Romania, Ocna Mureș | 1890-02-06 | -- | 1890–1911 | 2 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| Otta kulturhus | Otta kulturhus | Norway, Otta, Skansen 9 | 1993-03-07 | 2018-09-08 | 1993–2018 | 13 | |
| Old Auditorium, Worcester State College | Old Auditorium, Worcester State College | United States, Worcester, 486 Chandler Street | 1971-04-29 | 1971-05-01 | 1971 | 1 | |
| Oslo Rådhus | Oslo Rådhus | Norway, Oslo, Rådhusplassen 1 | 2009-03-28 | -- | 2009 | 1 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Ostseebad Göhren | Ostseebad Göhren | Germany, Göhren | 2010-05-04 | -- | 2010 | 1 | |
| OC Vondel (Ontmoetingscentrum Meulebeke) | OC Vondel (Ontmoetingscentrum Meulebeke) | Belgium, Meulebeke, Karel van Manderstraat 26 | 2002-02-28 | 2002-02-28 | 2002 | 1 | |
| Ohnsorg Theater | Ohnsorg Theater | Germany, Hamburg, Heidi-Kabel-Platz 1 | 1995-04-24 | 2002-05-25 | 1995–2002 | 2 | |
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Venues
