| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Old Tote Theatre, The | The Old Tote Theatre | Australia, Kensington, High Street | 1967-09-23 | 1971-08-03 | 1967–1971 | 2 | |
| Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Russia, Omsk, ul. Krasnyy Put' 153 | 2005-10-01 | -- | 2005 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Odd Duck Studio | Odd Duck Studio | United States of America, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| Opera House | Opera House | United States of America, Hopkinsville | 1904-11-23 | 1904-11-23 | 1904 | 1 | |
| Ōsakafu Tachi josei sōgō sentā | Ōsakafu Tachi josei sōgō sentā (Osaka Prefectural Women's Center) | Japan, 1 Chome-3-49 Otemae, Chuo Ward, Osaka, 540-0008 | 2006-11-10 | -- | 2006 | 1 | |
| Oslo | Oslo | Norway, Oslo | 1926-09-12 | 2008-10-02 | 1926–2014 | 10 | |
| Orikkusu Gekijō | Orikkusu Gekijō (Orix Theater) | Japan, Osaka, 1-14-15 Shin-machi, Nishi-ku | 1971-10-03 | -- | 1971 | 2 | |
| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Opera Comique Theatre | Opera Comique Theatre | England, London | 1889-07-17 | 1895-03-30 | 1889–1895 | 6 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Ontmoetingscentrum Aalbeke | Ontmoetingscentrum Aalbeke | Belgium, Aalbeke, Aalbekeplaats | 2001-03-12 | 2001-03-12 | 2001 | 1 | |
| Olde Towne Hall Theatre | Olde Towne Hall Theatre | United States of America, North Ridgeville, 36119 Center Ridge Road | 2018-05-18 | 2018-05-19 | 2018 | 1 | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Čeljabinsk | 1978-09- | -- | 1978 | 1 | |
| Oakland University | Oakland University | United States of America, Rochester, 2200 North Squirrel Road | 1972-03-02 | 1972-03-26 | 1972 | 1 | |
| Opernhaus, Städtische Theater Karl-Marx-Stadt | Städtische Theater Karl-Marx-Stadt (Opernhaus) | Germany, Karl-Marx-Stadt (Chemnitz), Theaterplatz | 1956-04-29 | -- | 1956 | 1 | |
| Opernhaus Hannover | Opernhaus Hannover | Germany, Hannover, Opernplatz 1 | 1928-03-06 | 1956-12-05 | 1928–1956 | 2 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
| Ocean Hotell | Ocean Hotell | Norway, Horten, Jernbanegata 1 | 2006-02-02 | -- | 2006 | 1 | |
| Optima Playhouse | Optima Playhouse | Australia, Adelaide, Festival Drive | 1999-07-06 | 1999-07-24 | 1999 | 1 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Orange Tree Theatre, The | The Orange Tree Theatre | England, London, 1 Clarence St, Richmond | 1991-10-10 | 2012-12-15 | 1991–2012 | 3 | |
| Opera House | Opera House | United States of America, Telluride | -- | -- | | | |
| Oriental Vevey | Oriental Vevey | Switzerland, Vevey, Rue d'Italie, 22 | 2018-10-31 | 2018-11-18 | 2018 | 2 | |
| Oldenburgisches Staatstheater | Oldenburgisches Staatstheater | Germany, Oldenburg, Theaterwall 28 | 1918-11-30 | 2015-12-20 | 1918–2015 | 12 | |
| Odyssée, L' | L'Odyssée | France, Périgueux, Esplanade Robert Badinter | 2017-01-12 | 2017-01-13 | 2017 | 1 | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo | 1994-08-23 | -- | 1994 | 1 | |
| Opera House | Opera House | United States of America, Wyoming, Wyoming | -- | -- | | | |
| Operahuset Nordfjord | Operahuset Nordfjord | Norway, Nordfjord, Sophus Lie-vegen 3 | 2009-11-09 | -- | 2009–2017 | 6 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Országos Kamaraszínház | Országos Kamaraszínház | Hungary, Mezőtúr | 1925-09-23 | -- | 1925–1927 | 2 | |
| Örkény István Színház | Örkény István Színház | Hungary, Budapest, Madách Imre tér 6 | 2012-03-17 | -- | 2012 | 1 | |
| Old globe theatre, the | The Old Globe Theatre | United States of America, San Diego, 1363 Old Globe Way | 1995-04-30 | 1995-06-18 | 1995 | 1 | |
| Opera House | Opera House | United States of America, Altoona | 1904-03-14 | 1904-03-14 | 1904 | 1 | |
| Orfeó Gracienc | Orfeó Gracienc | Spain, Barcelona, Carrer d'Astúries, 83 (Gràcia) | 1910-07- | -- | 1910–1915 | 2 | |
| Odense | Odense | Denmark, Odense | 1948-04-20 | -- | 1948–2000 | 2 | |
| Opera House | Opera House | United States of America, Detroit | 1896-02-18 | 1910-09-28 | 1896–1910 | 2 | |
| Ohio State University | Ohio State University | United States of America, Columbus, 1739 North High Street | 1981-02-27 | 2001-03-04 | 1981–2001 | 2 | |
| Opéra-Théâtre de Limoges | Opéra-Théâtre de Limoges | France, Limoges, 48 rue Jean Jaurès | 2017-05-09 | 2017-05-11 | 2017 | 1 | |
| Olivier Theatre | Olivier Theatre | England, Southbank, London, National Theatre, Upper Ground | 1978-04-25 | 2019-10-08 | 1978–2019 | 11 | |
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