| O`Brien-Moore, Erin | Erin O'Brien-Moore | Actor | 1923 - 1956 | 4 | |
| O`Neill, Aisling | Aisling O`Neill | Actor | 2001 | 1 | |
| O´Byrne, Louis | Louis O´Byrne | Designer | 1991 | 1 | |
| O´Connell, Dyan | Dyan O´Connell | Lighting Designer | 2005 | 1 | |
| O´Donnell, Sarah | Sarah O´Donnell | Actor | 1987 | 2 | |
| O´Donnell, Trisha | Trisha O´Donnell | Lighting Designer | 1981 | 1 | |
| O´Driscoll, Ann | Ann O´Driscoll | Director, Lighting Designer | 1985 | 2 | |
| O´Neill, Katherine | Katherine O´Neill | Actor | 2004 | 1 | |
| O´Neill, Noel | Noel O´Neill | Actor | 1979 | 1 | |
| O´Regan, Mark | Mark O´Regan | Actor | 1988 | 5 | |
| O´Valle, Violet | Violet O´Valle | Director | 2008 | 1 | |
| O' Mahony, Tom | Tom O' Mahony | Actor | 1979 | 1 | |
| O'Berski, Jay | Jay O'Berski | Actor | 2002 | 1 | |
| O'Berski, Jaybird | Jaybird O'Berski | Actor | 2018 | 1 | |
| O'Brady, Mary | Mary O'Brady | Director | 2018 | 1 | |
| O'Brian, Vana | Vana O'Brian | Actor | 2019 | 1 | |
| O'Brien, Adale | Adale O'Brien | Actor | 1961 - 1962 | 2 | |
| O'Brien, Barret | Barret O'Brien | Actor | 2008 | 1 | |
| O'Brien, Dan | Dan O'Brien | Designer, Lighting Designer | 2008 | 2 | |
| O'Brien, Daniel | Daniel O'Brien | Actor | 2012 | 1 | 1 |
| O'Brien, Denise | Denise O'Brien | Designer | 2023 | 1 | |
| O'Brien, Doc | Doc O'Brien | Actor | 1991 | 6 | |
| O'Brien, Eileen | Eileen O'Brien | Actor | 2000 | 8 | 1 |
| O'Brien, Ita | Ita O'Brien | Actor | 2005 | 1 | |
| O'Brien, Jack | Jack O'Brien | Director | 1990 - 2025 | 2 | 1 |
| O'Brien, Jackie | Jackie O'Brien | Actor | 2006 | 10 | |
| O'Brien, James | James O'Brien | Actor | 1957 - 1971 | 2 | |
| O'Brien, Jaye | Jaye O'Brien | Actor | 1957 | 1 | |
| O'Brien, Jim | Jim O'Brien | Actor | 2004 - 2021 | 2 | 1 |
| O'Brien, John | John O'Brien | Actor | 1970 | 1 | |
| O'Brien, Joseph | Joseph O'Brien | Actor | 1960 | 1 | |
| O'Brien, Kay | Kay O'Brien | Actor | 1945 | 1 | |
| O'Brien, Keith | Keith O'Brien | Musical Director | 2016 - 2019 | 2 | |
| O'Brien, Maurice | Maurice O'Brien | Actor | 1945 | 1 | |
| O'Brien, Meredith | Meredith O'Brien | Actor | 2022 | 1 | |
| O'Brien, Neal | Neal O'Brien | Actor | 2024 | 1 | |
| O'Brien, Patrick | Patrick O'Brien | Actor | 2006 | 1 | |
| O'Brien, Paul | Paul O'Brien | Actor | 1980 | 1 | |
| O'Brien, Peter | Peter O'Brien | Actor | 2002 | 1 | 1 |
| O'Brien, Peter | Peter O'Brien | Musician | 1982 | 1 | |
| O'Brien, Raymond | Raymond O'Brien | Actor | 1935 - 1937 | 7 | |
| O'Brien, Sean | Sean O'Brien | Actor | 1999 | 1 | |
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