| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| Opéra de Rouen | Opéra de Rouen | France, Rouen, 7 rue du Docteur Rambert | 2003-11-29 | 2003-11-30 | 2003 | 1 | |
| Oviedo | Oviedo | Spain | 1904-- | -- | 1904 | 1 | |
| Osobnyak Theatre | Osobnyak Theatre | Russia, St. Petersburg, Kamennoostrovsky 55 | 2011-05-15 | 2011-05-17 | 2011 | 1 | |
| Olten | Olten | Switzerland, Olten | 2003-02-17 | -- | 2003 | 1 | |
| Överkalix Folkets Hus | Överkalix Folkets Hus | Sweden, Överkalix, Bulandsgatan 2 | 2010-11-16 | -- | 2010 | 1 | |
| Oslo dagene, Akershus Festning | Oslo dagene, Akershus Festning | Norway, Oslo | 1983-08-29 | 1983-09-03 | 1983 | 1 | |
| Off Latina | Off Latina | Spain, Madrid, Calle de los Mancebos, 4 | 2019-11-07 | 2020-04-29 | 2019 | 1 | |
| Oravais Teater | Oravais Teater | Finland, Kimo, Oravais, Kyroboas Kvarn | 1996-07-11 | -- | 1996 | 1 | |
| O'Reilly Theatre | O'Reilly Theatre | Ireland, Dublin, Great Denmark Street | 2011-09-27 | 2011-10-16 | 2011 | 1 | |
| Ottumwa | Ottumwa | United States of America, Ottumwa | 1903-11-04 | 1903-11-04 | 1903 | 1 | |
| Olofström | Olofström | Sweden, Olofström | 1992-11-12 | -- | 1992 | 1 | |
| Obldramteatr | Obldramteatr | Russia, Ivanovo | 1940-03-24 | -- | 1940 | 1 | |
| Ontmoetingscentrum d'Iefte | Ontmoetingscentrum d'Iefte | Belgium, Deerlijk, Hoogstraat 122 | 2002-01-14 | 2002-01-15 | 2002 | 1 | |
| Ottawa Little Theatre Group | Ottawa Little Theatre Group | Canada, Ottawa | 1945-12-20 | -- | 1945 | 1 | |
| Oberlin College & Conservatory, Hall auditorium | Oberlin College & Conservatory | United States of America, Oberlin, 67 North Main St. | 2014-04-17 | 2014-04-19 | 2014 | 1 | |
| Opéra de Dijon | Opéra de Dijon | France, Dijon, 11 Boulevard de Verdun | 2014-03-10 | 2014-03-12 | 2014 | 1 | |
| Opernhaus Unter den Linden | Opernhaus Unter den Linden | Germany, Berlin | 1905-09-20 | -- | 1905 | 1 | |
| Óbudai Kisfaludy Színház | Óbudai Kisfaludy Színház | Hungary, Budapest | 1900-04-15 | -- | 1900 | 1 | |
| Oslo Nye teater | Oslo Nye Teater (Hovedscenen) | Norway, Oslo, Rosenkrantz' gate 10, Oslo, Norway | 2023-06-08 | 2023-08-24 | 2023 | 1 | |
| Opera House | Opera House | United States of America, Logan | 1905-04-15 | 1905-04-15 | 1905 | 1 | |
| Opera Națională București | Opera Națională București | Romania, Bucharest, Bulevardul Mihail Kogălniceanu 70-72 | 2007-05-09 | -- | 2007 | 1 | |
| Olavskapellet, Borgarsyssel Museum | Olavskapellet, Borgarsyssel Museum | Norway, Sarpsborg, Gamlebygaten 8 | 2006-08-01 | 2006-08-02 | 2006 | 1 | |
| Opera House | Opera House | United States of America, Pensacola | 1903-10-25 | 1903-10-25 | 1903 | 1 | |
| Opera House | Opera House | New Zealand, Wellington, 111/113 Manners Street | 1890-11-28 | 1890-11-29 | 1890 | 1 | |
| Opera House | Opera House | England, Coventry, 4 Hales Street | 1911-09-11 | 1911-09-14 | 1911 | 1 | |
| Oblastnoi dramteatr Volgograd | Oblastnoi dramteatr Volgograd | Russia, Volgograd | 1948-10- | -- | 1948 | 1 | |
| Opština Bečej | Opština Bečej | Serbia, Opština Bečej | 1903-03-11 | -- | 1903 | 1 | |
| Olomouc | Olomouc | Czech Republic, Olomouc | 2007-05-17 | -- | 2007 | 1 | |
| Opéra National de Lorraine | Opéra National de Lorraine | France, Nancy, 1 Rue Sainte-Catherine, | 2013-05-23 | -- | 2013 | 1 | |
| Overture Center for the Arts, The Playhouse | Overture Center for the Arts, The Playhouse | United States of America, Madison, 201 State St | 2010-03-18 | 2010-03-28 | 2010 | 1 | |
| Oda Tiyatrosu | Atatürk Kültür Merkezi Oda Tiyatrosu (AKM Oda Tiyatrosu) | Turkey, Istanbul, Gümüşsuyu Mahallesi, Tak-ı Zafer Cd., Beyoğlu | 1975-- | 1976-- | 1975 | 1 | |
| Opera House | Opera House | United States of America, San Juan | 1905-05-06 | 1905-05-06 | 1905 | 1 | |
| Ostersund | Ostersund | Sweden, Ostersund | 1936-10-30 | -- | 1936 | 1 | |
| Opera House | Opera House | United States of America, Bemidji | 1904-09-20 | 1904-09-20 | 1904 | 1 | |
| Oscarshall | Oscarshall | Norway, Oslo, Oscarshallveien | 2017-08-28 | 2017-11-28 | 2017 | 1 | |
| Oakland University | Oakland University | United States of America, Rochester, 2200 North Squirrel Road | 1972-03-02 | 1972-03-26 | 1972 | 1 | |
| Ostadetheater | Ostadetheater | Netherlands, Amsterdam | 1985-04-25 | -- | 1985 | 1 | |
| Opéra National de Lyon | Opéra National de Lyon | France, Lyon, 1 place de la Comédie | 2022-06-04 | 2022-06-13 | 2022 | 1 | |
| Odensbacken | Odensbacken | Sweden | 2002-09-12 | -- | 2002 | 1 | |
| Oden Hall | Oden Hall | United States of America, Dr, Gambier, 107 College | 2024-04-07 | 2024-04-07 | 2024 | 1 | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo | 1994-08-23 | -- | 1994 | 1 | |
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