| Old Rep at Birmingham Repertory Theatre | The Old Rep at Birmingham Repertory Theatre | England, Birmingham | 2013-03-14 | 2013-03-28 | 2013 | 1 | |
| Odda kino | Odda kino | Norway, Odda, Opheimsgata 31, 5750 ODDA | 1969-09-26 | -- | 1969–1978 | 4 | |
| Odensbacken | Odensbacken | Sweden | 2002-09-12 | -- | 2002 | 1 | |
| Odda | Odda | Norway, Odda | 1951-04-25 | 1958-03-02 | 1951–1982 | 6 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 1 | |
| Old globe theatre, the | The Old Globe Theatre | United States, San Diego, 1363 Old Globe Way | 1995-04-30 | 1995-06-18 | 1995 | 1 | |
| Opera House | Opera House | United States, Santa Cruz | 1905-07-28 | 1905-07-28 | 1905 | 1 | |
| Opéra national du Rhin | Opéra national du Rhin | France, Strasbourg, 19 place Broglie | 2020-09-19 | 2020-09-20 | 2020 | 1 | |
| Oosterpoort Groningen, De | De Oosterpoort Groningen | Netherlands, 9724 DA, Trompsingel 27, | 2000-04-20 | 2000-04-21 | 2000 | 1 | |
| Örebro | Örebro (Oerebro) | Sweden, Örebro | 1936-09-27 | -- | 1936–1970 | 3 | |
| Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Omskiy Gosudarstvennyy Dramaticheskiy Pyatyy Teatr | Russia, Omsk, ul. Krasnyy Put' 153 | 2005-10-01 | -- | 2005 | 1 | |
| Östersund | Östersund | Sweden, Östersund | 1879-- | -- | 1879 | 1 | |
| Oliver Theatre | Oliver Theatre | United States, Lincoln | 1903-05-09 | 1908-11-03 | 1903–1908 | 2 | |
| Odd Duck Studio | Odd Duck Studio | United States, Seattle, 1214 10th Avenue | 2008-11-26 | 2008-12-20 | 2008 | 1 | |
| Opera House | Opera House | United States, Hopkinsville | 1904-11-23 | 1904-11-23 | 1904 | 1 | |
| Operetten Neues Theater, Central Theater | Operetten Neues Theater, Central Theater | Germany, Leipzig | 1910-08-23 | 1910-08-30 | 1910 | 1 | |
| Olde Towne Hall Theatre | Olde Towne Hall Theatre | United States, North Ridgeville, 36119 Center Ridge Road | 2018-05-18 | 2018-05-19 | 2018 | 1 | |
| Östgötateatern | Östgötateatern | Sweden, Norrköping, Slottsgatan 135 | 1997-11-15 | 2022-03-19 | 1997–2022 | 2 | |
| Opera House | Opera House | United States, Kentucky, Kentucky | 1899-12-20 | 1903-12-10 | 1899–1903 | 2 | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Ontmoetingscentrum Aalbeke | Ontmoetingscentrum Aalbeke | Belgium, Aalbeke, Aalbekeplaats | 2001-03-12 | 2001-03-12 | 2001 | 1 | |
| Odsherred Teater | Odsherred Teater | Denmark, Nykobing Sjaelland, Annebergparken 22 | 2002-02-27 | -- | 2002–2006 | 2 | |
| Osservatorio, Teatro | Teatro Osservatorio | Italy, Bari, Trento 12 | 2017-05-07 | -- | 2017 | 1 | |
| Oslo Public Library | Oslo Public Library | Norway, Oslo, Arne Garborgs plass 4 | 1988-06-30 | -- | 1988 | 1 | |
| Oberschlesisches Grenzlandtheater Ratibor | Oberschlesisches Grenzlandtheater Ratibor | Poland, Ratibor / Racibórz | 1937-02-19 | -- | 1937 | 1 | |
| Örebro Teater | Örebro Teater | Sweden, Örebro, Storgatan 1 | 1876-09-23 | 1889-12-14 | 1876–1909 | 7 | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Čeljabinsk | 1980-09- | -- | 1980 | 1 | |
| Oslo Nye Teater (Centralteatret) | Oslo Nye Teater (Centralteatret) | Norway, Oslo, Akersgata 38 | 1972-09-28 | 2017-06-17 | 1972–2017 | 10 | |
| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Origosenteret | Origosenteret | Norway, Svinndal, Tyritoppen 19 | 2012-11-26 | -- | 2012 | 2 | |
| Offenburg Stadthalle | Offenburg Stadthalle | Germany, Offenburg, Schutterwälder Str. 3 | 1997-10-22 | 1997-10-22 | 1997 | 1 | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Orosháza | Orosháza | Hungary, Orosháza | 1890-05-12 | -- | 1890–1926 | 6 | |
| Opera House | Opera House | United States, Telluride | -- | -- | | | |
| Ocean Hotell | Ocean Hotell | Norway, Horten, Jernbanegata 1 | 2006-02-02 | -- | 2006 | 1 | |
| Oriental Vevey | Oriental Vevey | Switzerland, Vevey, Rue d'Italie, 22 | 2018-10-31 | 2018-11-18 | 2018 | 2 | |
| Opernhaus, Städtische Theater Karl-Marx-Stadt | Städtische Theater Karl-Marx-Stadt (Opernhaus) | Germany, Karl-Marx-Stadt (Chemnitz), Theaterplatz | 1956-04-29 | -- | 1956 | 1 | |
| Old Tote Theatre, The | The Old Tote Theatre | Australia, Kensington, High Street | 1967-09-23 | 1971-08-03 | 1967–1971 | 2 | |
| Örkény István Színház | Örkény István Színház | Hungary, Budapest, Madách Imre tér 6 | 2012-03-17 | -- | 2012 | 1 | |
| Opernhaus | Opernhaus | Germany, Wuppertal, Kurt-Drees-Straße 4 | 2011-06-26 | 2011-12-01 | 2011 | 2 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
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