| Oslo fengsel | Oslo fengsel | Norway, Oslo, Åkebergveien 11 | 2012-11-27 | -- | 2012 | 2 | |
| Oslo Domkirke | Oslo Domkirke | Norway, Oslo, Karl Johans gate 11 | 2018-02-09 | 2018-02-10 | 2018 | 1 | |
| Oslo dagene, Akershus Festning | Oslo dagene, Akershus Festning | Norway, Oslo | 1983-08-29 | 1983-09-03 | 1983 | 1 | |
| Oslo | Oslo | Norway, Oslo | 1926-09-12 | 2008-10-02 | 1926–2014 | 10 | |
| Oskarshamn | Oskarshamn | Sweden, Oskarshamn | 1991-05-03 | 1991-05-03 | 1991–1992 | 2 | |
| Oskar-Herbig-Halle | Oskar-Herbig-Halle | Germany, Mellrichstadt, Bahnhofstr. 17 | 2004-03-03 | -- | 2004–2011 | 2 | |
| Osimo | Osimo | Italy | -- | -- | | | |
| Oseberg Kulturhus | Oseberg Kulturhus | Norway, Tønsberg, Ollebukta 3 | 2008-03-08 | 2008-10-10 | 2008–2009 | 3 | |
| Oseana Kunst & Kultursenter | Oseana Kunst & Kultursenter | Norway, Os, Mobergsbakken 20 | 2012-09-18 | 2020-09-13 | 2012–2020 | 5 | |
| OSCO - Open Space Hannover | OSCO - Open Space Hannover | Germany, Hannover, Fössestraße 103 | 2019-11-14 | 2019-11-17 | 2019 | 1 | |
| Oscarshall | Oscarshall | Norway, Oslo, Oscarshallveien | 2017-08-28 | 2017-11-28 | 2017 | 1 | |
| Oscarsborg Festning | Oscarsborg Festning | Norway, Oscarsborg, Husvikveien | 2006-07-27 | 2007-06-24 | 2006–2007 | 2 | |
| Oscar Theatre | Oscar Theatre | Ireland, Dublin | 1980-04-07 | 1980-04-19 | 1980 | 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 | |
| Ōsaka Chikamatsu-za | Ōsaka Chikamatsu-za (Chikamatsuza Theatre) | Japan, Osaka | 1913-11-21 | 1913-11-25 | 1913 | 1 | |
| Országos Kamaraszínház | Országos Kamaraszínház | Hungary, Mezőtúr | 1925-09-23 | -- | 1925–1927 | 2 | |
| Orpheum Theatre | Orpheum Theatre | United States of America, Salt Lake City | 1908-06-13 | 1908-06-13 | 1908 | 1 | |
| Orpheum | Orpheum | United States of America, El Paso | 1908-06-18 | 1908-06-18 | 1908 | 1 | |
| Orpheum | Orpheum | Germany, Munich | 1893-03-08 | -- | 1893–1895 | 3 | |
| Orosháza | Orosháza | Hungary, Orosháza | 1890-05-12 | -- | 1890–1926 | 6 | |
| Ornö | Ornö | Sweden, Ornö | -- | -- | | | |
| Ornans | Ornans | France, Ornans | -- | -- | | | |
| Orlovskij dramatičeskij teatr imeni I. Turgeneva | Orlovskij dramatičeskij teatr imeni I. Turgeneva | Russia, Orel, Orel | 1944-05- | -- | 1944–1964 | 2 | |
| Orleneff’s Russian Lyceum | Orleneff’s Russian Lyceum | United States of America, New York, East Third Street | 1906-01-03 | -- | 1906 | 1 | |
| Orkdal Samfunnshus | Orkdal Samfunnshus | Norway, Fannrem | 1978-11-22 | -- | 1978 | 1 | |
| Orkdal Kulturhus | Orkdal Kulturhus | Norway, Orkanger, Allfarveg 7300 | 2012-11-11 | 2020-10-29 | 2012–2020 | 5 | |
| Orkanger gymnas | Orkanger gymnas | Norway, Orkanger | 1970-02-13 | -- | 1970 | 1 | |
| Orkanger | Orkanger | Norway, Orkanger | 1958-01-23 | -- | 1958–2005 | 5 | |
| Orikkusu Gekijō | Orikkusu Gekijō (Orix Theater) | Japan, Osaka, 1-14-15 Shin-machi, Nishi-ku | 1971-10-03 | -- | 1971 | 2 | |
| Origosenteret | Origosenteret | Norway, Svinndal, Tyritoppen 19 | 2012-11-26 | -- | 2012 | 2 | |
| Oriental Vevey | Oriental Vevey | Switzerland, Vevey, Rue d'Italie, 22 | 2018-10-31 | 2018-11-18 | 2018 | 2 | |
| Orfeó Gracienc | Orfeó Gracienc | Spain, Barcelona, Carrer d'Astúries, 83 (Gràcia) | 1910-07- | -- | 1910–1915 | 2 | |
| ORF Radio (Austria) | ORF Radio (Austria) | Austria | 1991-04-18 | -- | 1991 | 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 | |
| Orchard Theatre, the | The Orchard Theatre | England, Dartford, Home Gardens | 1996-03-12 | 1996-03-16 | 1996 | 1 | |
| Oravița | Oravița | Romania, Oravița | 1884-12-08 | 1884-12-23 | 1884–1913 | 3 | |
| Oravice | Oravice | Slovak Republic, Oravice | -- | -- | | | |
| Oravais Teater | Oravais Teater | Finland, Kimo, Oravais, Kyroboas Kvarn | 1996-07-11 | -- | 1996 | 1 | |
| Orăștie | Orăștie | Romania, Orăștie | 1911-02-16 | -- | 1911 | 1 | |
| Oranjerie | Oranjerie | Netherlands, Roermond, Kloosterwandplein 12-16 | 2009-11-07 | -- | 2009 | 1 | |
| Oranienburg | Oranienburg | Germany, Oranienburg | -- | -- | | | |
| Orange Tree Theatre, The | The Orange Tree Theatre | England, London, 1 Clarence St, Richmond | 1991-10-10 | 2012-12-15 | 1991–2012 | 3 | |
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