| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Odessa | Одеса (Odessa) | Ukraine, Odessa | -- | -- | | | |
| Ogra | Ogra | Romania, Ogra | -- | -- | | | |
| Oppdal | Oppdal | Norway, Oppdal | -- | -- | | | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Odder | Odder | Denmark, Odder | -- | -- | | | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Oituz | Oituz | Romania, Oituz | -- | -- | | | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Opera House | Opera House | United States, Telluride | -- | -- | | | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Opole | Opole | Poland, Opole | -- | -- | | | |
| Ostrava | Ostrava | Czech Republic, Ostrava | -- | -- | | | |
| Obârşia | Obârşia | Romania, Obârşia | -- | -- | | | |
| Ocna Sibiului | Ocna Sibiului | Romania, Ocna Sibiului | -- | -- | | | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Opera House | Opera House | United States, New Castle | 1907-03-09 | 1907-03-09 | 1907 | 1 | |
| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| OPERATTEN im STATTtheater | OPERATTEN im STATTtheater | Switzerland, Stäfa, Bahnhofstrasse 52 | 2007-03-07 | 2007-04-21 | 2007 | 1 | |
| Olofström | Olofström | Sweden, Olofström | 1992-11-12 | -- | 1992 | 1 | |
| OC Vondel (Ontmoetingscentrum Meulebeke) | OC Vondel (Ontmoetingscentrum Meulebeke) | Belgium, Meulebeke, Karel van Manderstraat 26 | 2002-02-28 | 2002-02-28 | 2002 | 1 | |
| Oberlin College & Conservatory, Hall auditorium | Oberlin College & Conservatory | United States, Oberlin, 67 North Main St. | 2014-04-17 | 2014-04-19 | 2014 | 1 | |
| Oranjerie | Oranjerie | Netherlands, Roermond, Kloosterwandplein 12-16 | 2009-11-07 | -- | 2009 | 1 | |
| Oslo dagene, Akershus Festning | Oslo dagene, Akershus Festning | Norway, Oslo | 1983-08-29 | 1983-09-03 | 1983 | 1 | |
| Old Town Players | Old Town Players | United States, Chicago | 1973-02-09 | 1973-04-15 | 1973 | 1 | |
| Oddemarka skole | Oddemarka skole | Norway, Kristiansand, Kristiansand | 2006-11-08 | -- | 2006 | 1 | |
| Olathe Opera House | Olathe Opera House | United States, Olathe | 1908-01-31 | 1908-01-31 | 1908 | 1 | |
| Opera House | Opera House | United States, Pensacola | 1903-10-25 | 1903-10-25 | 1903 | 1 | |
| Otto-Klenert-Schule | Otto-Klenert-Schule | Germany, Bad Friedrichshall, Rathausplatz 7 | 2006-02-18 | -- | 2006 | 1 | |
| Ottumwa | Ottumwa | United States, Ottumwa | 1903-11-04 | 1903-11-04 | 1903 | 1 | |
| Odeon | Odeon | Argentina, Buenos Aires | 1904-06-24 | 1904-06-26 | 1904 | 1 | |
| Oblastnoi dramteatr Volgograd | Oblastnoi dramteatr Volgograd | Russia, Volgograd | 1948-10- | -- | 1948 | 1 | |
| Obshtinski teatar Vazrazhdane | Obshtinski teatar Vazrazhdane | Bulgaria, Sofia, Sq. Petko Slaveykov 4 (пл. Петко Р. Славейков 4) | 1996-11-30 | -- | 1996 | 1 | |
| Ottawa Little Theatre Group | Ottawa Little Theatre Group | Canada, Ottawa | 1945-12-20 | -- | 1945 | 1 | |
| O'Connell Theatre | O'Connell Theatre | United States, Dekalb, Stevens Building, School of Theatre and Dance Northern Illinois University | 2009-02-19 | 2009-03-01 | 2009 | 1 | |
| Opera Națională București | Opera Națională București | Romania, Bucharest, Bulevardul Mihail Kogălniceanu 70-72 | 2007-05-09 | -- | 2007 | 1 | |
| OC De Buiting | OC De Buiting (Cultuur, gemeenschaps of ontmoetingscentrum) | Belgium, Beringen, Tessenderlosesteenweg 18 | 2007-11-29 | 2007-11-30 | 2007 | 1 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Oberammergau, Passionstheater | Passionstheater Oberammergau | Germany, Oberammergau, Othmar-Weis-Str. | 2016-07-01 | 2016-07-23 | 2016 | 1 | |
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