| O'Riordan, Rachel | Rachel O'Riordan | Director | 2015 - 2020 | 3 | |
| O'Riada, Sean | Sean O'Riada | Composer | 1961 | 1 | |
| O'Reilly, Vincent, A. | Vincent A. O'Reilly | Adaptation, Director | 2012 | 2 | 1 |
| O'Reilly, Sheila | Sheila O'Reilly | Actor | 1945 | 1 | |
| O'Reilly, John | John O'Reilly | Actor | 1983 | 3 | |
| O'Reilly, James | James O'Reilly | Actor | 1981 | 2 | |
| O'Reilly, Imelda | Imelda O'Reilly | Actor | 1990 | 1 | |
| O'Reilly, Genevieve | Genevieve O'Reilly | Actor | 2011 | 1 | 2 |
| O'Reilly, Ciarán | Ciarán O'Reilly | Director | 2008 | 1 | 1 |
| O'Reilly, Alpho | Alpho O'Reilly | Actor | 1948 | 1 | |
| O'Nians, Honor | Honor O'Nians | Designer | 1945 - 1946 | 2 | |
| O'Nians, Betty | Betty O'Nians | Actor | 1954 | 1 | |
| O'Neill, Vincent | Vincent O'Neill | Actor | 2009 | 1 | |
| O'Neill, Norman | Norman O'Neill | Composer | 1913 | 1 | |
| O'Neill, Noreen | Noreen O'Neill | Actor | 2011 | 1 | 1 |
| O'Neill, Molly | Molly O'Neill | Actor | 1993 | 1 | |
| O'Neill, Michelle | Michelle O'Neill | Actor | 2008 | 3 | |
| O'Neill, Luke | Luke O'Neill | Actor | 2006 | 1 | |
| O'Neill, Kathleen | Kathleen O'Neill | Actor | 1904 | 1 | |
| O'Neill, Katherine | Katherine O'Neill | Choreographer | 2004 | 1 | |
| O'Neill, Errol | Errol O'Neill | Actor | 1989 | 1 | 1 |
| O'Neill, Desmond | Desmond O'Neill | Actor | 1961 | 1 | |
| O'Neill, Denis | Denis O'Neill | Actor | 1936 | 1 | |
| O'Neill, Dean | Dean O'Neill | Actor | 1993 | 1 | |
| O'Neill, Daniel | Daniel O'Neill | Actor | 2013 | 1 | |
| O'Neill, Chris | Chris O'Neill | Designer, Lighting Designer | 2011 | 2 | |
| O'Neill, Aron, Arnarson | Aron Arnarson O'Neill | Actor | 2012 | 1 | |
| O'Neil, Ted | Ted O'Neil | Actor | 2009 | 1 | |
| O'Neil, Sally | Sally O'Neil | Actor | 1939 | 1 | |
| O'Neil, Rebecca Pugh Parker | Rebecca Pugh Parker O'Neil | Actor | 2023 | 1 | |
| O'Neil, Raymond | Raymond O'Neil | Actor | 2000 | 1 | |
| O'Neil, Randall | Randall O'Neil | Designer | 1948 | 1 | |
| O'Neil, Nance | Nance O'Neil | Actor | 1900 - 1917 | 23 | 1 |
| O'Neil, Barry | Barry O'Neil | Director | 1909 | 1 | |
| O'Neal, Timothy | Timothy O'Neal | Actor | 2006 | 1 | |
| O'Mara, Mollie | Mollie O'Mara | Actor | 1993 | 1 | |
| O'Mara, Kate | Kate O'Mara | Actor | 1981 | 1 | |
| O'Malley, Tom | Tom O'Malley | Actor | 1949 | 4 | |
| O'Malley, Geraldine | Geraldine O'Malley | Costume Designer, Designer | 1989 - 1990 | 4 | |
| O'Malley, Flynn | Flynn O'Malley | Actor | 1963 | 1 | |
| O'Malley, Cathleen | Cathleen O'Malley | Assistant Director | 2022 | 1 | |
| O'Mahony, Paul | Paul O'Mahony | Designer | 2013 - 2017 | 3 | |
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