Illustrators
- Michael O'Clery 1
- Eilis O'Connell 1
- Pixie O'Harris 1
- Hugh O'Neill 2
- John P. O'Neill 1
- Tom O'Reilly 2
- Terry Oakes 1
- Graham Oakley 13
- Y. Oda 1
- Alice M. Odgers 1
- Angela Ogden 3
- John Ogilby 1
- Carol Ogilvie 2
- James S. Ogilvy 1
- Ogle 5
- Richard Ogle 1
- Richard B. Ogle 1
- Jose G. Ojados 1
- Frank Oldham 1
- Olinda 1
- Tony Oliver 1
- Clara Olmstead 1
- Lola Onslow 1
- Olive F. Openshaw 16
- Winfried Opgenoorth 1
- E.R. Ord 1
- Giulia Orecchia 2
- Jan Ormerod 3
- Jean-Paul Orpinas 1
- Cecil Orr 1
- Jack Orr 4
- Monro S. Orr 1
- Stewart Orr 6
- Robert Osborn 1
- D. Osborne 1
- Rex Osborne 1
- Edward Osmond 2
- B. Ostertag 1
- Paul Ott 1
- J.B. Oudry 1
- R.F. Outcault 3
- Ida Rentoul Outhwaite 9
- W.H. Overend 4
- T.J. Overnell 2
- Ivan Owen 1
- Ivor Owen 1
- Juliette A. Owen 1
- W. Owen 1
- Will Owen 1
- Gail Owens 1
- Marjorie Owens 2
- Helen Oxenbury 7