Authors
- Gilda O'Neill
- H.C. O'Neill
- Hugh O'Neill
- Jane O'Neill
- Joan O'Neill
- Joe O'Neill
- John O'Neill
- John P. O'Neill 2
- Jonjo O'Neill
- Judith O'Neill
- Mary O'Neill
- Michael O'Neill
- Moira O'Neill
- N. O'Neill
- Norman O'Neill
- P.G. O'Neill
- Paul O'Neill
- R. O'Neill
- R.J. De C. O'Neill
- Raymond O'Neill
- Richard O'Neill
- Robert O'Neill
- T.P. O'Neill
- Terence O'Neill
- Timothy P. O'Neill
- William L. O'Neill
- N.J. O'Nion
- Paul O'Prey
- O'Rahilly
- Alfred O'Rahilly
- M. O'Reilley
- Pat O'Reilley
- Bernard O'Reilly
- Catherine M. O'Reilly
- Charles O'Reilly
- Francis Augustin O'Reilly
- John O'Reilly
- M. O'Reilly
- Mrs Robert O'Reilly 1
- Mrs. O'Reilly
- Pat O'Reilly
- Peter O'Reilly
- Sean O'Reilly
- Tim O'Reilly
- Tom O'Reilly 1
- Max O'Rell
- Michael O'Riordan
- Timothy O'Riordan
- R. O'Rouke
- G.G. O'Rourke
- Joseph O'Rourke
- P.J. O'Rourke
- O'Shaughnessy
- Hugh O'Shaughnessy
- John O'Shaughnessy
- N.J. O'Shaughnessy
- Brian O'Shea
- John M. O'Shea
- Pat O'Shea
- Richard O'Shea
- Tim O'Shea
- Micheal O'Sidahail
- Darlene O'Steen
- O'Sull
- Peter O'Sullevan
- Con O'Sullivan
- Deirdre O'Sullivan
- Donal O'Sullivan
- John O'Sullivan 1
- Maurice O'Sullivan
- Patricia O'Sullivan 1
- Patrick O'Sullivan
- Paul O'Sullivan
- Pete O'Sullivan
- Seumas O'Sullivan
- Timothy O'Sullivan
- Tyrone O'Sullivan
- Vincent O'Sullivan
- Margaret O'Sweeten
- Christopher O'Toole
- E.H O'Toole
- John O'Toole
- Laurence O'Toole
- Peter O'Toole
- Rev. P.L. O'Toole
- Tom O'Toole
- O'Tunader
- Shay Oag
- David Oakden
- E.C. Oakden
- Ralph Oakden
- E.M. Oakeley
- Alma Oakes
- Clifford Oakes
- Peter Oakes 1
- Roger A. Oakes
- Tony Oakes
- Michael Oakeshott
- R. Ewart Oakeshott
- W.F. Oakeshott