Authors
- Finnian O Cionnaith 1
- Patrick O'Brian 5
- Conor Cruise O'Brien 1
- Eileen O'Casey 1
- Daniel O'Connor 2
- Frank O'Connor 1
- Mike O'Connor 4
- Patrick J. O'Connor 3
- Raymond J. O'Connor 1
- Terry O'Connor 1
- Norrey Jephson O'Conor 1
- Roy O'Dell 2
- Brendan O'Donoghue 1
- Eileen O'Faolain 1
- Mervyn O'Gorman 1
- K.T. O'Grady 1
- Kane O'Hara 1
- Colette O'Hare 2
- Cleophas C. O'Harra 1
- Paul O'Keeffe 1
- Michael O'Leary 3
- Tony O'Mahony 1
- B.H. St. J. O'Neil 1
- Pat O'Reilly 1
- Tom O'Reilly 1
- John O'Sullivan 1
- Patricia O'Sullivan 1
- E.R. Oakley 2
- Graham Oakley 3
- Michael Oakley 1
- Joan Oates 1
- L.C. Ockenden 2
- Martin Odersky 1
- Sally Farrell Odgers 1
- Waclaw Odyniec 1
- Richard Offner 1
- Christopher Ogborne 1
- Angela Ogden 2
- Bob Ogden 1
- Charles Ogden 2
- J. Douglas Ogilby 1
- Malcolm A. Ogilvie 1
- Will H. Ogilvie 4
- David Ogilvy 1
- James S. Ogilvy 1
- Miles K. Oglethorpe 1
- Bob Ogley 1
- Hideaki Ohba 1
- Jane Ohlmeyer 2
- Thomas Okey 1
- Charles S. Olcott 1
- Jenny Oldfield 1
- Katharine Oldmeadow 3
- Michel Oleffe 7
- Laurie Olin 1
- Achille Bonito Oliva 1
- W.H.T. Olive 1
- Charles E. Oliver 1
- David Oliver 2
- George Oliver 1
- Jennie A. Oliver 1
- Jocelyn Oliver 1
- Michael Oliver 1
- Thomas Oliver 1
- Torfrida Oliver 1
- Henry Olivier 1
- Jean Moulin Ollagnier 1
- Peter Ollerhead 1
- Don Olney 1
- John Andreas Olsen 1
- Klaus Malling Olsen 2
- Lars-Henrik Olsen 1
- Gary D. Olson 1
- James S. Olson 1
- Roberta J.M. Olson 1
- Storrs L. Olson 1
- Henrik Olsson 1
- Frank Olynyk 1
- Jacqueline Onassis 1
- Hans Onderwater 1
- Stephen Ongpin 1
- Willem Oosthoek 1
- Iona Opie 8
- Peter Opie 4
- Leslie Oppitz 1
- Hiawyn Oram 1
- Doris Orgel 1
- Benedetta Origo 1
- Christopher Orlebar 1
- Laszlo Orloci 1
- John David Orme 1
- Elizabeth Ormerod 1
- G. Wareing Ormerod 1
- Jan Ormerod 2
- Sarah Ormerod 1
- Ierne Ormsby 1
- William Orpen 1
- David B. Orr 1
- David R. Orr 1
- Adolfo Orsi 1