| Name | Functions  | Event Dates | Events | Resources | ||
|---|---|---|---|---|---|---|
| Želimir Orešković | Director | 1975 - 1989 | 3 | 1 | ||
| Aleksandar Ognjanović | Director | 1955 - 1979 | 4 | |||
| Herbert Olschok | Director | 1988 - 2014 | 5 | |||
| Marshall Oglesby | Director | 1973 | 1 | |||
| Matúš Oľha | Director | 1993 | 1 | |||
| Janet Owusu | Director | 2006 | 1 | 1 | ||
| Timo Ojala | Director | 1985 | 1 | |||
| Jack O'Brien | Director | 1990 - 2025 | 2 | 1 | ||
| David Oswald | Director | 1993 | 1 | |||
| S. Orlac | Director | 1995 | 1 | |||
| Warwick Ongley | Director | 1969 | 1 | |||
| Vera Oelschlegel | Director | 1997 - 2000 | 52 | |||
| Tim Ocel | Director | 2002 | 1 | |||
| Robert A. O'Connell | Director | 2003 | 1 | |||
| Cigdem Onat | Director | 2005 | 1 | |||
| Stefan Otteni | Director | 2006 | 1 | |||
| Violet O´Valle | Director | 2008 | 1 | |||
| Charles Otte | Director | 2008 | 1 | 1 | ||
| Ciarán O'Reilly | Director | 2008 | 1 | 1 | ||
| Katja Ott | Director | 2010 | 1 | |||
| Michael O’Neill | Director | 2010 | 1 | |||
| Klaus Opilik | Director | 2011 | 1 | |||
| Anca Ovanez Doroşenco | Director | 1968 | 1 | |||
| David Oliver | Director | 2012 | 1 | 1 | ||
| Pedro Orthous | Director | 1962 | 1 | |||
| Jessica Osbourne | Director | 2013 | 1 | |||
| Yasushi Ohki | Director | 1955 - 1956 | 2 | |||
| Shiro Okakura | Director | 1953 | 1 | |||
| Larry O'Dwyer | Director | 1970 | 1 | |||
| Pavel Ondruch | Director | 2016 | 1 | |||
| Richard O'Connell | Director | 1947 | 2 | |||
| Eugenie O'Sullivan | Director | 1949 | 1 | |||
| Ann Oakley | Director | 2000 | 1 | |||
| Grischa Ostrovski | Director | 1980 | 1 | |||
| Susan P. O'Hearn | Director | 2018 | 1 | |||
| Charlie Oates | Director | 2018 | 1 | |||
| Mary O'Brady | Director | 2018 | 1 | |||
| Gust Ongyerth | Director | 1940 | 1 | |||
| Shuji Onodera | Director | 2013 | 1 | |||
| Anne Occhiogrosso | Director | 2019 | 1 | |||
| Rachel O'Riordan | Director | 2015 - 2025 | 4 | |||
| Gumrah Omar | Director | 2019 | 1 | |||