| Orenstein, Joan | Joan Orenstein | Actor | 1981 – 1989 | 3 | |
| Ogier, Bulle | Bulle Ogier | Actor | 1993 | 4 | |
| Oswald, David | David Oswald | Director | 1993 | 1 | |
| Oswald, Birgit | Birgit Oswald | Actor | 1993 | 1 | |
| O'Brien, Tony | Tony O'Brien | Actor | 1993 | 1 | |
| Obst, Dietmar | Dietmar Obst | Actor | 1993 | 2 | |
| Okazaki, Shinobu | Shinobu Okazaki | Designer | 1991 | 1 | |
| Ohsawa, Kaoru | Kaoru Ohsawa | Lighting Designer | 1991 | 1 | |
| Obrecht, Urs | Urs Obrecht | Actor | 1991 | 1 | |
| Overloop, Veerle van | Veerle van Overloop | Actor | 1993 | 1 | |
| Ollinger, Hans | Hans Ollinger | Actor | 1993 | 1 | |
| Ochlast, Jens | Jens Ochlast | Actor | 1993 – 2015 | 3 | |
| Oberholz, Dieter | Dieter Oberholz | Actor | 1993 | 3 | |
| Ottosson, Annelie | Annelie Ottosson | Actor | 1993 | 2 | |
| Oskam, Floor | Floor Oskam | Designer | 1991 – 1992 | 14 | |
| Overbeeke, Adri | Adri Overbeeke | Actor | 1991 – 1992 | 84 | |
| Ottlik, Ádám | Ádám Ottlik | Actor | 1996 | 2 | |
| Orthmann, Ruth | Ruth Orthmann | Translator | 1994 | 1 | |
| Ott, Friederike | Friederike Ott | Actor | 2014 – 2016 | 12 | |
| Oikonomidou, Miranta | Miranta Oikonomidou | Actor | 1965 – 1994 | 4 | |
| Oliver, Stephen | Stephen Oliver | Composer | 1977 – 1982 | 9 | |
| Ortmayr, Heinrich | Heinrich Ortmayr | Actor | 1982 | 1 | |
| Okhlupin, Igor | Igor Okhlupin (Игорь Охлупин) | Actor | 2013 | 1 | |
| Oberle, Carl-Friedrich | Carl-Friedrich Oberle | Costume Designer, Designer | 1994 | 2 | |
| Oliveira, Vidal de | Vidal de Oliveira | Translator | 1949 – 1955 | 6 | |
| Olszewska, Izabella | Izabella Olszewska | Actor | 1994 | 1 | |
| Oliver, Tim | Tim Oliver | Sound Designer | 1994 – 1995 | 3 | |
| O'Connor, Frances | Frances O'Connor | Actor | 1994 | 1 | |
| O'Sullivan, Barney | Barney O'Sullivan | Actor | 1976 – 1980 | 2 | |
| Ogawa, Shinji | Shinji Ogawa | Actor | 1980 | 1 | |
| Oug , Linda | Linda Oug | Actor | 1980 | 1 | |
| O'Donoghue, Brian | Brian O'Donoghue | Lighting Designer | 1980 | 1 | |
| O'Brien , Paul | Paul O'Brien | Actor | 1980 | 1 | |
| Ostan, Boris | Boris Ostan | Actor | 1994 | 1 | |
| Ostan Vejrup, Jette | Jette Ostan Vejrup | Actor | 1994 | 1 | |
| Osmond, David | David Osmond | Actor | 2012 | 1 | |
| O'Connor, Francis | Francis O'Connor | Designer | 2000 | 1 | |
| Ohshima, Nobuhisa | Nobuhisa Ohshima | Actor, Adaptation, Director | 1994 | 3 | |
| O'Kane, Patrick | Patrick O'Kane | Actor | 2000 | 1 | |
| Oman, Julia , Trevelyan | Julia Trevelyan Oman | Designer | 1980 | 1 | |
| Odegard, Julia | Julia Odegard | Actor | 1980 | 1 | |
| Oglesby, Thomas | Thomas Oglesby | Actor | 1977 | 2 | |
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