| Oldenburgisches Staatstheater | Oldenburgisches Staatstheater | Germany, Oldenburg, Theaterwall 28 | 1918-11-30 | 2015-12-20 | 1918–2015 | 12 | |
| Opera House | Opera House | United States of America, Hopkinsville | 1904-11-23 | 1904-11-23 | 1904 | 1 | |
| Opernzelt | Opernzelt | Germany, Heidelberg, Emil-Maier-Straße 16 | 2011-04-29 | 2011-07-05 | 2011 | 1 | |
| Oslo Nye Dukketeater | Oslo Nye Dukketeater | Norway, Oslo | 1994-08-23 | -- | 1994 | 1 | |
| Opera House | Opera House | United States of America, Concord | 1909-04-22 | 1909-04-22 | 1909 | 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 | |
| Odda yrkesskule | Odda yrkesskule | Norway, Odda | 1970-01-23 | -- | 1970 | 1 | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Open Space Theatre | Open Space Theatre | United States of America, New York | 1982-01-11 | -- | 1982 | 1 | |
| Odense | Odense | Denmark, Odense | 1948-04-20 | -- | 1948–2000 | 2 | |
| Odeon-Theater | Odeon-Theater | Germany, Goslar, Bismarckstraße 1 | 1997-10-10 | 1997-10-10 | 1997–2005 | 2 | |
| 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 | |
| Odeïon | Odeïon | Austria, Salzburg/Langwied, Waldorfstraße 13 | 2013-09-26 | 2013-10-27 | 2013 | 1 | |
| Ordway Center for the Performing Arts (Main Hall) | Ordway Center for the Performing Arts (Main Hall) | United States of America, Saint Paul, 345 Washington St | 2005-10-18 | 2005-10-19 | 2005 | 1 | |
| Opera House | Opera House | United States of America, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Opernhaus Graz | Opernhaus Graz | Austria, Graz, Opernring | 1912-05-24 | -- | 1912 | 2 | |
| Operettenhaus | Operettenhaus | Germany, Düsseldorf, Jahnstraße | 1952-11-01 | -- | 1952 | 1 | |
| Origosenteret | Origosenteret | Norway, Svinndal, Tyritoppen 19 | 2012-11-26 | -- | 2012 | 2 | |
| Opera House | Opera House | United States of America, San Bernardino | 1903-12-31 | 1908-12-04 | 1903–1908 | 2 | |
| Opera House | Opera House | United States of America, Racine | 1903-05-06 | 1903-05-06 | 1903 | 1 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Ohio State University | Ohio State University | United States of America, Columbus, 1739 North High Street | 1981-02-27 | 2001-03-04 | 1981–2001 | 2 | |
| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Čeljabinsk | 1978-09- | -- | 1978 | 1 | |
| Opéra-Théâtre i Avignon | Opéra-Théâtre i Avignon | France, Avignon, 1 Rue Racine | 2012-07-18 | 2012-07-25 | 2012 | 1 | |
| OPERATTEN im STATTtheater | OPERATTEN im STATTtheater | Switzerland, Stäfa, Bahnhofstrasse 52 | 2007-03-07 | 2007-04-21 | 2007 | 1 | |
| Oriental Vevey | Oriental Vevey | Switzerland, Vevey, Rue d'Italie, 22 | 2018-10-31 | 2018-11-18 | 2018 | 2 | |
| Osnabrücker Hof | Osnabrücker Hof | Germany, Osnabrück, Kollegienwall 14 | 1896-05-13 | -- | 1896 | 1 | |
| Old Tote Theatre, The | The Old Tote Theatre | Australia, Kensington, High Street | 1967-09-23 | 1971-08-03 | 1967–1971 | 2 | |
| Opera House | Opera House | United States of America, New Castle | 1907-03-09 | 1907-03-09 | 1907 | 1 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Odense Teater | Odense Teater | Denmark, Odense, Jernbanegade 21 | 1928-04-30 | 2025-11-22 | 1928–2025 | 18 | |
| Other Place, The | The Other Place | England, Stratford-upon-Avon, Warwickshire, Waterside | 1981-07-06 | 1982-07-30 | 1981–1996 | 4 | |
| Oerlenbach | Oerlenbach | Germany, Oerlenbach | 2009-12-19 | -- | 2009 | 1 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States of America, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| OC Vondel (Ontmoetingscentrum Meulebeke) | OC Vondel (Ontmoetingscentrum Meulebeke) | Belgium, Meulebeke, Karel van Manderstraat 26 | 2002-02-28 | 2002-02-28 | 2002 | 1 | |
| Orfeó Gracienc | Orfeó Gracienc | Spain, Barcelona, Carrer d'Astúries, 83 (Gràcia) | 1910-07- | -- | 1910–1915 | 2 | |
| Oslo dagene, Akershus Festning | Oslo dagene, Akershus Festning | Norway, Oslo | 1983-08-29 | 1983-09-03 | 1983 | 1 | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| Ódry Színpad | Ódry Színpad | Hungary, Budapest, Vas utca 2 | 1967-12-16 | -- | 1967–2017 | 3 | |
| Orpheum | Orpheum | United States of America, El Paso | 1908-06-18 | 1908-06-18 | 1908 | 1 | |
| O'Reilly Theatre | O'Reilly Theatre | Ireland, Dublin, Great Denmark Street | 2011-09-27 | 2011-10-16 | 2011 | 1 | |
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