| Ozoliņš, Pēteris | Pēteris Ozoliņš | Actor, Director | 1889 - 1912 | 5 | |
| Outram, Leonard | Leonard Outram | Actor, Director | 1891 - 1897 | 7 | 1 |
| Odemar, Fritz | Fritz Odemar | Actor, Director | 1893 - 1934 | 5 | |
| Osmarr, Otto | Otto Osmarr | Actor, Director | 1889 - 1919 | 23 | |
| Oikonomou, Thomas | Thomas Oikonomou | Actor, Director | 1902 - 1926 | 121 | |
| Ognjanov, Sava | Sava Ognjanov | Actor, Director | 1905 - 1928 | 8 | |
| Orlenev, Pavel | Pavel Orlenev | Actor, Director | 1903 - 1923 | 14 | 1 |
| Ones, Arvid | Arvid Ones | Actor, Director | 1983 - 2004 | 22 | 1 |
| Osis, Jānis | Jānis Osis | Actor, Director | 1921 - 1943 | 5 | |
| Oden, Christopher | Christopher Oden | Actor, Director | 1984 - 2001 | 6 | 1 |
| Oliver, Barbara | Barbara Oliver | Actor, Director | 2006 - 2010 | 3 | 1 |
| Olsen, Arne, Thomas | Arne Thomas Olsen | Actor, Director | 1955 - 1963 | 19 | 1 |
| Olsen, Clifford, R. | Clifford R. Olsen | Actor, Director | 1963 | 2 | 1 |
| O'Connell, Moya | Moya O'Connell | Actor, Director | 2012 - 2024 | 2 | 1 |
| O'Connell, Dan | Dan O'Connell | Actor, Director | 1943 - 1961 | 2 | |
| Orell, Heinrich | Heinrich Orell | Actor, Director | 1911 | 2 | |
| Osterberg, Craig | Craig Osterberg | Actor, Designer, Lighting Designer | 2009 | 3 | |
| Otto, Alexander | Alexander Otto | Actor, Designer | 1919 - 1966 | 7 | |
| Olisah, Paul | Paul Olisah | Actor, Designer | 2002 | 2 | |
| Ovaska, Sulo | Sulo Ovaska | Actor, Designer | 1956 | 2 | |
| O’Hearn, Robert | Robert O’Hearn | Actor, Designer | 1949 - 1950 | 3 | |
| Opgaard, John | John Opgaard | Actor, Designer | 1939 | 2 | |
| Oftedahl, Ole | Ole Oftedahl | Actor, Dancer | 1928 | 2 | |
| Ocampo, Paul | Paul Ocampo | Actor, Dancer | 2001 | 2 | |
| Olympios, Spyros | Spyros Olympios | Actor, Dancer | 1935 - 1997 | 10 | |
| Olsson, Yean | Yean Olsson | Actor, Costume Designer | 1997 | 4 | |
| O'Rourke, Joan | Joan O'Rourke | Actor, Costume Designer | 1945 - 1961 | 4 | |
| Olsen, Ole | Ole Olsen | Actor, Composer | 1895 - 1922 | 18 | 2 |
| Olsen, Max | Max Olsen | Actor, Composer | 1987 | 2 | |
| Oliver, Stephen | Stephen Oliver | Actor, Composer | 1977 - 2024 | 10 | |
| Osazuwa, Evelyn, Rasmussen | Evelyn Rasmussen Osazuwa | Actor, Composer | 2018 - 2019 | 4 | |
| O’Connell, Sara | Sara O’Connell | Actor, Choreographer, Dancer | 2004 | 4 | |
| O'Mahoney, Robert | Robert O'Mahoney | Actor, Author | 1982 - 1991 | 10 | |
| Olinescu, Boris | Boris Olinescu | Actor, Assistant Director | 1959 | 2 | |
| Opstad, Peder | Peder Opstad | Actor, Adaptation, Director, Producer | 2005 - 2010 | 183 | |
| Oliveira, Domingos, José Soares de | Domingos José Soares de Oliveira | Actor, Adaptation, Director, Lighting Designer, Sound Designer, Translator | 1983 - 1998 | 15 | |
| Op gen Orth, Helga | Helga Op gen Orth | Actor, Adaptation, Director | 1992 - 1996 | 4 | |
| Ohshima, Nobuhisa | Nobuhisa Ohshima | Actor, Adaptation, Director | 1994 | 3 | |
| Olson, Niclas | Niclas Olson | Actor, Adaptation, Director | 2017 | 3 | |
| Oswald, Karin | Karin Oswald | Actor, Adaptation | 2007 | 2 | |
| Odeen-Isbister, Sara | Sara Odeen-Isbister | Actor, Adaptation | 2020 | 2 | |
| Oudrey, Pierre | Pierre Oudrey | Actor | 1973 | 1 | |
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