R
- Edna O'Brien (born 1932?)
- Joseph O'Connor (born 1963)
- Philip Ó Ceallaigh
- Liam O'Flaherty (1896–1984)
- Brian O'Nolan (1912–1966) (writing as Flann O'Brien; journalistic pseudonym Myles na gCopaleen)
- Sean O'Reilly (born 1969)
- TS O'Rourke (born 1968)
- Glenn Patterson (born 1961)
- James Plunkett (1920–2003)
- Keith Ridgway (born 1965)
- Frank Ronan (born 1963)
Read more about this topic: List Of Irish Novelists, O