| Oblastnoi dramatičeskij teatr | Oblastnoi dramatičeskij teatr | Russia, Veliky Novgorod | 1948-09- | -- | 1948 | 1 | |
| Odda ungdomsskole | Odda ungdomsskole | Norway, Odda, Eidesmoen | 2006-11-15 | -- | 2006 | 1 | |
| Odsherred Teater | Odsherred Teater | Denmark, Nykobing Sjaelland, Annebergparken 22 | 2002-02-27 | -- | 2002–2006 | 2 | |
| Overholser Theatre | Overholser Theatre | United States of America, Ardmore | 1910-12-21 | 1910-12-21 | 1910 | 1 | |
| Örebro Teater | Örebro Teater | Sweden, Örebro, Storgatan 1 | 1876-09-23 | 1889-12-14 | 1876–1909 | 8 | |
| Opera Națională București | Opera Națională București | Romania, Bucharest, Bulevardul Mihail Kogălniceanu 70-72 | 2007-05-09 | -- | 2007 | 1 | |
| Oulu | Oulu | Finland, Oulu | -- | -- | | | |
| Open Space Theatre | Open Space Theatre | United States of America, New York | 1982-01-11 | -- | 1982 | 1 | |
| Open Scene Orlando (Instagram) | Open Scene Orlando (Instagram) | United States of America, Orlando | 2020-05-07 | 2020-06-10 | 2020 | 1 | |
| OC De Neerbeek | OC De Neerbeek (Ontmoetingscentrum De Neerbeek) | Belgium, Bissegem, Vlaswaagplein 1 | 2002-01-10 | 2002-01-10 | 2002–2007 | 2 | |
| Oddfellows' Hall | Oddfellows' Hall | Australia, Wagga Wagga, Fitzmaurice Street | -- | -- | | | |
| Old Courthouse | Old Courthouse | Northern Ireland, Antrim, Market Square | 2011-05-26 | -- | 2011 | 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 | England, Coventry, 4 Hales Street | 1911-09-11 | 1911-09-14 | 1911 | 1 | |
| Opéra National de Lorraine | Opéra National de Lorraine | France, Nancy, 1 Rue Sainte-Catherine, | 2013-05-23 | -- | 2013 | 1 | |
| Origosenteret | Origosenteret | Norway, Svinndal, Tyritoppen 19 | 2012-11-26 | -- | 2012 | 2 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 1 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Opéra national du Rhin | Opéra national du Rhin | France, Strasbourg, 19 place Broglie | 2020-09-19 | 2020-09-20 | 2020 | 1 | |
| Opera House | Opera House | United States of America, Concord | 1909-04-22 | 1909-04-22 | 1909 | 1 | |
| Opernhaus | Opernhaus | Germany, Wuppertal, Kurt-Drees-Straße 4 | 2011-06-26 | 2011-12-01 | 2011 | 2 | |
| Ostersund | Ostersund | Sweden, Ostersund | 1936-10-30 | -- | 1936 | 1 | |
| Old Tote Theatre, The | The Old Tote Theatre | Australia, Kensington, High Street | 1967-09-23 | 1971-08-03 | 1967–1971 | 2 | |
| Oliver Theatre | Oliver Theatre | United States of America, Lincoln | 1903-05-09 | 1908-11-03 | 1903–1908 | 2 | |
| Odorheiu Secuiesc | Odorheiu Secuiesc | Romania, Odorheiu Secuiesc | 1911-05-09 | -- | 1911 | 1 | |
| Opera House | Opera House | United States of America, Hopkinsville | 1904-11-23 | 1904-11-23 | 1904 | 1 | |
| Odeon-Theater | Odeon-Theater | Germany, Goslar, Bismarckstraße 1 | 1997-10-10 | 1997-10-10 | 1997–2005 | 2 | |
| Otto-Klenert-Schule | Otto-Klenert-Schule | Germany, Bad Friedrichshall, Rathausplatz 7 | 2006-02-18 | -- | 2006 | 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 | |
| Opera House | Opera House | United States of America, McCook | 1905-03-16 | 1905-03-16 | 1905 | 1 | |
| Opernhaus | Opernhaus | Germany, Frankfurt, Opernplatz 1 | 1892-12-10 | -- | 1892–1940 | 2 | |
| Octagon, The | The Octagon | United States of America, Montgomery, 1 Festival Drive | 1997-03-04 | 2002-04-14 | 1997–2002 | 2 | |
| Opera House | Opera House | United States of America, San Bernardino | 1903-12-31 | 1908-12-04 | 1903–1908 | 2 | |
| Opernhaus | Opernhaus | Germany, Essen | 1942-04-19 | -- | 1942 | 1 | |
| Oscarshall | Oscarshall | Norway, Oslo, Oscarshallveien | 2017-08-28 | 2017-11-28 | 2017 | 1 | |
| Ostróg | Ostróg | Poland, Ostróg | -- | -- | | | |
| 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 | |
| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Oblastnoj teatr dramy | Oblastnoj teatr dramy | Russia, Čeljabinsk | 1978-09- | -- | 1978 | 1 | |
| OPERATTEN im STATTtheater | OPERATTEN im STATTtheater | Switzerland, Stäfa, Bahnhofstrasse 52 | 2007-03-07 | 2007-04-21 | 2007 | 1 | |
| OC Westrand | OC Westrand | Belgium, Dilbeek, Kamerijklaan z/n | 1994-04-14 | -- | 1994–2004 | 4 | |
| Opera House | Opera House | United States of America, New Castle | 1907-03-09 | 1907-03-09 | 1907 | 1 | |
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