Illustrators
- Michael O'Clery 1
- Eilis O'Connell 1
- Hugh O'Neill 2
- Martin O'Neill 1
- Tom O'Reilly 2
- Graham Oakley 7
- Y. Oda 1
- Angela Ogden 3
- Carol Ogilvie 2
- Sara Ogilvie 1
- James S. Ogilvy 1
- Ogle 5
- Richard B. Ogle 2
- Jose G. Ojados 1
- Frank Oldham 1
- Olinda 1
- Tony Oliver 1
- Clara Olmstead 1
- Derek J. Onley 1
- Lola Onslow 1
- Olive F. Openshaw 15
- Winfried Opgenoorth 1
- Giulia Orecchia 2
- Jan Ormerod 6
- Jean-Paul Orpinas 1
- Jack Orr 4
- Monro S. Orr 1
- Stewart Orr 5
- 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 11
- W.H. Overend 4
- T.J. Overnell 2
- Ivan Owen 1
- Juliette A. Owen 1
- W. Owen 1
- Will Owen 2
- Gail Owens 1
- Marjorie Owens 3
- Helen Oxenbury 7
- Oxley 1