| Otieno, Mercy Dorcas | Mercy Dorcas Otieno | Actor | 2021 | 2 | |
| Obinu, Gianfranco Onatziro | Gianfranco Onatziro Obinu | Actor | 2015 - 2019 | 3 | |
| Ori, Benedetta | Benedetta Ori | Actor | 1999 | 2 | |
| Orlandini, Veronica | Veronica Orlandini | Actor | 2015 | 1 | |
| Olivari, Michela | Michela Olivari | Actor | 2018 | 1 | |
| Olmedo, Darinka | Darinka Olmedo | Actor | 2024 | 1 | |
| Owen, Constance | Constance Owen | Actor | 2024 | 1 | |
| Otrębski , Grzegorz | Grzegorz Otrębski | Actor | 2022 | 1 | |
| Otterson, Jed | Jed Otterson | Actor | 2024 | 1 | |
| O’Leary, Helen | Helen O’Leary | Actor | 2018 | 1 | |
| Oswald, Karin | Karin Oswald | Actor, Adaptation | 2007 | 2 | |
| Odeen-Isbister, Sara | Sara Odeen-Isbister | Actor, Adaptation | 2020 | 2 | |
| 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 | |
| Oliveira, Domingos, José Soares de | Domingos José Soares de Oliveira | Actor, Adaptation, Director, Lighting Designer, Sound Designer, Translator | 1983 - 1998 | 15 | |
| Opstad, Peder | Peder Opstad | Actor, Adaptation, Director, Producer | 2005 - 2010 | 183 | |
| Olinescu, Boris | Boris Olinescu | Actor, Assistant Director | 1959 | 2 | |
| O'Mahoney, Robert | Robert O'Mahoney | Actor, Author | 1982 - 1991 | 10 | |
| O’Connell, Sara | Sara O’Connell | Actor, Choreographer, Dancer | 2004 | 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 | |
| Olsson, Yean | Yean Olsson | Actor, Costume Designer | 1997 | 4 | |
| O'Rourke, Joan | Joan O'Rourke | Actor, Costume Designer | 1945 - 1961 | 4 | |
| 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 | |
| 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 | |
| Osterberg, Craig | Craig Osterberg | Actor, Designer, Lighting Designer | 2009 | 3 | |
| Okornicki, Kazimierz | Kazimierz Okornicki | Actor, Director | 1908 - 1922 | 7 | |
| Ottbert, Otto | Otto Ottbert | Actor, Director | 1876 - 1906 | 7 | |
| Otto, Harald | Harald Otto | Actor, Director | 1896 - 1922 | 55 | 1 |
| Ourth, Georges | Georges Ourth | Actor, Director | 1978 - 1984 | 2 | |
| Ording, Jørn | Jørn Ording | Actor, Director | 1938 - 1978 | 69 | 1 |
| O'Connell, Deirdre | Deirdre O'Connell | Actor, Director | 1971 - 1985 | 6 | |
| Oskui, Mahin | Mahin Oskui | Actor, Director | 1959 | 2 | 1 |
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