Click for key
| O | Book and author | Other notes |
| Olive | Olive, the Other Reindeer by J. Otto Seibold | |
| Oliver Ollie | Tales of Oliver Pig by Jean Van Leeuwen The Wish Factory by Chris Riddell Oliver and the Monsters by Tony Blundell Oliver and Patch by Claire Freedman Oliver and the Seawigs by Philip Reeve Oliver Moon books by Sue Mongredien Harry Potter books by J. K. Rowling A Dog Called Flow by Pippa Goodhart A Werewolf Named Oliver James by Nicholas John Frith Oliver Twist by Charles Dickens McTavish books by Meg Rosoff | S S H, ! |
| Olivia (see also Livvy) | Olivia by Ian Falconer The Balloon Cloud by Clare Hanlon Wonder by R.J. Palacio (known as Via) | |
| Omar | Everybody Feels Scared by Moira Butterfield Planet Omar: Accidental Trouble Magnet by Zanib Mian | |
| Omri | The Indian in the Cupboard books by Lynne Reid Banks | S |
| Oonagh | Finn McCool stories (trad.) | |
| Orlando | Orlando the Marmalade Cat by Kathleen Hale | S |
| Orville | Penguinaut! by Marcie Colleen | |
| Oscar | Oscar the Hungry Unicorn by Lou Carter That Pesky Rat by Lauren Child Friends by Rob Lewis | |
| Otto | Otto the Book Bear by Katie Cleminson | |
| Ottoline | Ottoline and the Yellow Cat by Chris Riddell | S |
| Owen | Owen by Kevin Henkes A Mummy for Owen by Marion Dane Bauer (based on a true story) | ! |
