| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Allfarveg 7300 | 2012-11-11 | 2020-10-29 | 2012–2020 | 5 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Odsherred Teater | Odsherred Teater | Denmark, Nykobing Sjaelland, Annebergparken 22 | 2002-02-27 | -- | 2002–2006 | 2 | |
| Odeon Theatre | Odeon Theatre | United States, St. Louis | 1905-10-04 | 1912-03-27 | 1905–1912 | 2 | |
| Ocna Mureș | Ocna Mureș | Romania, Ocna Mureș | 1890-02-06 | -- | 1890–1911 | 2 | |
| Örebro Teater | Örebro Teater | Sweden, Örebro, Storgatan 1 | 1876-09-23 | 1889-12-14 | 1876–1909 | 7 | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Novosibirsk, Bol'shevistskaya Ulitsa, 45 | 1987-11- | -- | 1987 | 1 | |
| Old Courthouse | Old Courthouse | Northern Ireland, Antrim, Market Square | 2011-05-26 | -- | 2011 | 1 | |
| Obfelden | Obfelden | Switzerland | 2002-04-21 | -- | 2002 | 1 | |
| Odeïon | Odeïon | Austria, Salzburg/Langwied, Waldorfstraße 13 | 2013-09-26 | 2013-10-27 | 2013 | 1 | |
| Odda ungdomsskole | Odda ungdomsskole | Norway, Odda, Eidesmoen | 2006-11-15 | -- | 2006 | 1 | |
| Ouagadougou, Carrefour Internationale de Théâtre de Ouagadougou | Carrefour Internationale de Théâtre de Ouagadougou | Burkina Faso, Bilbalogho, Ouagadougou, Burkina Faso | 2002-07-13 | -- | 2002 | 1 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Overholser Theatre | Overholser Theatre | United States, Ardmore | 1910-12-21 | 1910-12-21 | 1910 | 1 | |
| Opština Bečej | Opština Bečej | Serbia, Opština Bečej | 1903-03-11 | -- | 1903 | 1 | |
| Ocean Hotell | Ocean Hotell | Norway, Horten, Jernbanegata 1 | 2006-02-02 | -- | 2006 | 1 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| OC De Neerbeek | OC De Neerbeek (Ontmoetingscentrum De Neerbeek) | Belgium, Bissegem, Vlaswaagplein 1 | 2002-01-10 | 2002-01-10 | 2002–2007 | 2 | |
| Odenkirchen | Odenkirchen | Germany, Odenkirchen | 1893-10-07 | -- | 1893 | 1 | |
| Opera House | Opera House | United States, Wyoming, Wyoming | -- | -- | | | |
| Opernhaus | Opernhaus | Germany, Wuppertal, Kurt-Drees-Straße 4 | 2011-06-26 | 2011-12-01 | 2011 | 2 | |
| Oslo Rådhus | Oslo Rådhus | Norway, Oslo, Rådhusplassen 1 | 2009-03-28 | -- | 2009 | 1 | |
| Opera House | Opera House | United States, Detroit | 1896-02-18 | 1910-09-28 | 1896–1910 | 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 | |
| Opera House | Opera House | United States, Concord | 1909-04-22 | 1909-04-22 | 1909 | 1 | |
| Otta Samfunnshus | Otta Samfunnshus | Norway, Otta, Klyphaugvegen 8, 2670 Otta | 1973-09-30 | -- | 1973–1987 | 4 | |
| Opernhaus | Opernhaus | Germany, Frankfurt, Opernplatz 1 | 1892-12-10 | -- | 1892–1940 | 2 | |
| Opera House | Opera House | United States, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Olivenza | Olivenza | Spain, Olivenza | -- | -- | | | |
| Opernhaus | Opernhaus | Germany, Essen | 1942-04-19 | -- | 1942 | 1 | |
| Oblastnoi dramatičeskij teatr | Oblastnoi dramatičeskij teatr | Russia, Veliky Novgorod | 1948-09- | -- | 1948 | 1 | |
| Överkalix Folkets Hus | Överkalix Folkets Hus | Sweden, Överkalix, Bulandsgatan 2 | 2010-11-16 | -- | 2010 | 1 | |
| Odeon-Theater | Odeon-Theater | Germany, Goslar, Bismarckstraße 1 | 1997-10-10 | 1997-10-10 | 1997–2005 | 2 | |
| Owl Spot | Owl Spot | Japan, Tokyo | 2009-02-04 | 2016-11-23 | 2009–2016 | 7 | |
| Opera Theatre | Opera Theatre | France, Limoges, 48, Rue Jean-jaurès | 2017-05-09 | 2017-05-11 | 2017 | 1 | |
| Oakland University | Oakland University | United States, Rochester, 2200 North Squirrel Road | 1972-03-02 | 1972-03-26 | 1972 | 1 | |
| Ornans | Ornans | France, Ornans | 2001-- | -- | 2001 | 1 | |
| Old Vic, The | The Old Vic | England, London, The Cut | 1922-03-06 | 2016-03-19 | 1922–2016 | 11 | |
| Ophelia Theater | Ophelia Theater | United States, Astoria, 21-12 30th Road | 2016-10-28 | 2016-11-13 | 2016 | 1 | |
| OC Westrand | OC Westrand | Belgium, Dilbeek, Kamerijklaan z/n | 1994-04-14 | -- | 1994–2004 | 4 | |
| Opera House | Opera House | United States, San Bernardino | 1903-12-31 | 1908-12-04 | 1903–1908 | 2 | |
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