| Orsky, Gudrun | Gudrun Orsky | Director | 2004 | 1 | |
| Ott, Sharon | Sharon Ott | Director | 1993 - 1997 | 3 | |
| Orsza-Łukasiewicz, Janina | Janina Orsza-Łukasiewicz | Director | 1972 | 1 | |
| Oittinen, Tytti | Tytti Oittinen | Director | 1992 - 1994 | 2 | |
| O'Connor, John | John O'Connor | Director | 2003 | 1 | |
| Orlandini, Claudio | Claudio Orlandini | Director | 2011 | 1 | |
| Ochandiano, Amelia | Amelia Ochandiano | Director | 2010 - 2011 | 40 | |
| O'Leary, Bridget Kathleen | Bridget Kathleen O'Leary | Director | 2011 | 1 | |
| Oscar, Harry | Harry Oscar | Director | 1900 | 1 | |
| Oberländer, Hans | Hans Oberländer | Director | 1904 - 1908 | 2 | |
| O'Neil, Barry | Barry O'Neil | Director | 1909 | 1 | |
| Osanai, Kaoru | Kaoru Osanai | Director | 1909 - 1928 | 6 | |
| Olafsen, Carl Fredrik | Carl Fredrik Olafsen | Director | 2010 | 1 | |
| Ostrowsky, Hartmut | Hartmut Ostrowsky | Director | 1975 | 1 | |
| Orešković, Želimir | Želimir Orešković | Director | 1975 - 1989 | 3 | |
| Ognjanović, Aleksandar | Aleksandar Ognjanović | Director | 1955 - 1979 | 4 | |
| Olschok, Herbert | Herbert Olschok | Director | 1988 - 2014 | 5 | |
| Oglesby, Marshall | Marshall Oglesby | Director | 1973 | 1 | |
| Oľha, Matúš | Matúš Oľha | Director | 1993 | 1 | |
| Owusu, Janet | Janet Owusu | Director | 2006 | 1 | |
| Ojala, Timo | Timo Ojala | Director | 1985 | 1 | |
| O'Brien, Jack | Jack O'Brien | Director | 1990 | 1 | |
| Oswald, David | David Oswald | Director | 1993 | 1 | |
| Orlac, S. | S. Orlac | Director | 1995 | 1 | |
| Ongley, Warwick | Warwick Ongley | Director | 1969 | 1 | |
| Oelschlegel, Vera | Vera Oelschlegel | Director | 1997 - 2000 | 52 | |
| Ocel, Tim | Tim Ocel | Director | 2002 | 1 | |
| O'Connell, Robert, A. | Robert A. O'Connell | Director | 2003 | 1 | |
| Onat, Cigdem | Cigdem Onat | Director | 2005 | 1 | |
| Otteni, Stefan | Stefan Otteni | Director | 2006 | 1 | |
| O´Valle, Violet | Violet O´Valle | Director | 2008 | 1 | |
| Otte, Charles | Charles Otte | Director | 2008 | 1 | |
| O'Reilly, Ciarán | Ciarán O'Reilly | Director | 2008 | 1 | |
| Ott, Katja | Katja Ott | Director | 2010 | 1 | |
| O’Neill, Michael | Michael O’Neill | Director | 2010 | 1 | |
| Opilik, Klaus | Klaus Opilik | Director | 2011 | 1 | |
| Ovanez Doroşenco, Anca | Anca Ovanez Doroşenco | Director | 1968 | 1 | |
| Oliver, David | David Oliver | Director | 2012 | 1 | |
| Orthous, Pedro | Pedro Orthous | Director | 1962 | 1 | |
| Osbourne, Jessica | Jessica Osbourne | Director | 2013 | 1 | |
| Ohki, Yasushi | Yasushi Ohki | Director | 1955 - 1956 | 2 | |
| Okakura, Shiro | Shiro Okakura | Director | 1953 | 1 | |
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