| Oakeshott, Owen | Owen Oakeshott | Actor | 2013 - 2014 | 11 | 1 |
| Oakes, Tom | Tom Oakes | Actor | 2004 | 1 | |
| Oakes, Simeon | Simeon Oakes | Actor | 2012 | 1 | |
| Oakes, Robert | Robert Oakes | Adaptation | 2009 | 1 | |
| Oakes, Andrew | Andrew Oakes | Actor | 2016 | 1 | |
| Oaker, Jane | Jane Oaker | Actor | 1904 | 1 | 1 |
| Oakenleaf, Fingal | Fingal Oakenleaf | Actor | 2008 | 1 | |
| Oak, Girija | Girija Oak | Translator | 2009 | 1 | |
| O’Shaughnessy, Hilary | Hilary O’Shaughnessy | Actor | 2011 | 2 | |
| O’Rowe, Mark | Mark O’Rowe | Adaptation, Director | 2015 - 2023 | 2 | |
| O’Rourke, Rylee | Rylee O’Rourke | Assistant Director, Producer | 2020 - 2022 | 2 | |
| O’Neill, Michael | Michael O’Neill | Director | 2010 | 1 | |
| O’Keefe, Brian | Brian O’Keefe | Costume Designer | 2009 | 1 | |
| O’Hearn, Robert | Robert O’Hearn | Actor, Designer | 1949 - 1950 | 3 | |
| O’Hearn, Nigel | Nigel O’Hearn | Adaptation | 2011 - 2016 | 4 | |
| O’Connor, Francis | Francis O’Connor | Set Designer | 2023 | 1 | |
| O’Connell, Will | Will O’Connell | Actor | 2011 | 2 | |
| O’Connell, Sara | Sara O’Connell | Actor, Choreographer, Dancer | 2004 | 4 | |
| O’Clery, Joan | Joan O’Clery | Costume Designer | 2023 | 1 | |
| O’Brien, Scott | Scott O’Brien | Composer | 2001 | 1 | |
| O’Brien, Peter | Peter O’Brien | Costume Designer | 2015 | 1 | |
| O’Brien, Fergus | Fergus O’Brien | Sound Designer | 2006 | 9 | |
| O’Brien, Brad | Brad O’Brien | Actor | 2010 | 1 | |
| O'Wisiedo, Mayrata | Mayrata O'Wisiedo | Actor | 1968 | 1 | |
| O'Toole, John | John O'Toole | Actor | 1987 - 2000 | 2 | |
| O'Sullivan, Rob | Rob O'Sullivan | Actor | 2024 | 1 | |
| O'Sullivan, Pat | Pat O'Sullivan | Lighting Designer | 1964 | 1 | |
| O'Sullivan, Matthew | Matthew O'Sullivan | Actor | 1984 | 1 | |
| O'Sullivan, Mathew | Mathew O'Sullivan | Actor | 1969 | 1 | |
| O'Sullivan, Eugenie | Eugenie O'Sullivan | Director | 1949 | 1 | |
| O'Sullivan, Barney | Barney O'Sullivan | Actor | 1976 - 1980 | 2 | |
| O'Sullivan, Anne | Anne O'Sullivan | Actor | 2012 | 1 | |
| O'Sullivan IV, John | John O'Sullivan IV | Actor | 2013 | 1 | |
| O'Shea, Ryan | Ryan O'Shea | Actor | 2008 | 1 | |
| O'Shea, Milo | Milo O'Shea | Actor | 1961 | 1 | |
| O'Shea, James | James O'Shea | Actor | 1905 | 1 | |
| O'Shaughnessy, Fiona | Fiona O'Shaughnessy | Actor | 2008 | 2 | |
| O'Shannon, Finnuala | Finnuala O'Shannon | Actor | 1961 | 1 | |
| O'Rowe, Mark | Mark O'Rowe | Adaptation | 2016 | 1 | 1 |
| O'Rourke, Kristen | Kristen O'Rourke | Actor | 2009 | 1 | |
| O'Rourke, Joan | Joan O'Rourke | Actor, Costume Designer | 1945 - 1961 | 4 | |
| O'Rorke, Elle | Elle O'Rorke | Actor | 2006 | 1 | |
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