Illustrators – O
- Eve O'Brien 3 books
- John O'Brien 2 books
- Sean O'Brien 6 books
- Tara O'Brien 2 books
- Seán Ó’Brógáin 7 books
- Chelsea O'Byrne 3 books
- Nicola O'Byrne 14 books
- David O'Connell 32 books
- Sophia O'Connor 6 books
- Aoife J O'Dwyer 3 books
- Kate O’Hara 4 books
- Lauren O'Hara 12 books
- Helen O'Higgins 2 books
- Alejandro O'Keeffe 2 books
- Bryan Lee O'Malley 10 books
- Donough O'Malley 4 books
- Gillian Eilidh O’Mara 3 books
- Matt O'Neil 3 books
- Brooke O'Neill 2 books
- Eamonn O’Neill 4 books
- K. O'Neill 6 books
- Kelly O’Neill 3 books
- Kevin O'Neill 8 books
- Lauren O'Neill 5 books
- Alan O'Rourke 3 books
- Ellie O'Shea 17 books
- Juliana Oakley 7 books
- Ron Oaks 2 books
- Fumio Obata 2 books
- Takeshi Obata 52 books
- Elizabeth Ruth Obbard 3 books
- Karen Obuhanych 4 books
- Jose Luis Ocana 2 books
- Ocean 4 books
- Douma Oda 2 books
- Çağrı Odabaşı 3 books
- Odone 12 books
- Michael Avon Oeming 5 books
- Suharu Ogawa 2 books
- Sara Ogilvie 38 books
- Max A. Oginni 2 books
- Susie Oh 2 books
- Ei Ohitsuji 4 books
- Zachariah OHora 5 books
- Julius Ohta 6 books
- Ine Ohtaka 2 books
- Yoshitoki Oima 5 books
- Tugce Okay 5 books
- Takashi Okazaki 2 books
- Okdong 3 books
- Shu Okimoto 5 books
- Chinyere Okoroafor 3 books
- Ella Okstad 22 books
- Mutsumi Okubashi 4 books
- Akira Okubo 5 books
- Hiromasa Okujima 5 books
- Rachel Oldfield 6 books
- Liz Oldmeadow 4 books
- Mark Oldroyd 3 books
- Igor Oleynikov 2 books
- Carlos Javier Olivares 2 books
- Alvaro Oliveira 2 books
- Catarina Oliveira 2 books
- Helda Oliveira 2 books
- Marc Olivent 2 books
- Alison Oliver 12 books
- Ben Oliver 2 books
- Juanbjuan Oliver 8 books
- Ariel Olivetti 2 books
- Grasya Oliyko 6 books
- Darcie Olley 6 books
- Pat Olliffe 2 books
- Russell Olson 2 books
- Olympia Olympitis 2 books
- Alaba Onajin 3 books
- Onedove 2 books
- Melina Ontiveros 2 books
- Takafumi Oomae 5 books
- Jerome Opeña 3 books
- Emi Ordas 4 books
- Antonio Ordonez 2 books
- Miguel Ordonez 4 books
- Giulia Orecchia 6 books
- ORKA 4 books
- Asia Orlando 4 books
- Jade Orlando 10 books
- Jane Ormes 6 books
- Constanza Oroza 2 books
- Jose-Luis Orozco 2 books
- Richard Orr 2 books
- Jamie Orrell 7 books
- Anika Orrock 2 books
- Mirelle Ortega 9 books
- Nathalie Ortega 11 books
- Jesuso Ortiz 3 books
- Jose Ortiz 3 books
- Lydia Ortiz 3 books
- Davide Ortu 25 books
- Fiona Osbaldstone 4 books
- Kelsey Oseid 4 books
- James Oses 4 books
- Natalia Jimenez Osorio 2 books
- Sofia Ossman 4 books
- Pete Oswald 31 books
- Sole Otero 3 books
- Susan Ottaviano 2 books
- Matt Ottley 2 books
- Ryan Ottley 16 books
- Siya Oum 2 books
- Denys Ovenden 2 books
- Georgien Overwater 2 books
- Zhanna Ovocheva 6 books
- Clare Owen 5 books
- Sion Tomos Owen 2 books
- Su Owen 2 books
- Helen Oxenbury 49 books
- Christina Oyebade 4 books
- Devika Oza 2 books
- Zeynep Ozatalay 5 books
- Büşra Türeli Özçelik 6 books
- Berk Öztürk 5 books
