| Orban | France | 2 |
| Orbit | Angleterre | 893 |
| Orca Book Publishers | France | 9 |
| Orchard Books | Angleterre | 53 |
| Ordalaget Bokförlag | Suède | 14 |
| Orenda books | Angleterre | 19 |
| Orep | France | 45 |
| Organic | | 4 |
| Organisation des Nations Unies (ONU) | | 3 |
| Orients | | 4 |
| Original Books | France | 23 |
| Original Watts | France | 5 |
| Originale | | 1 |
| Orion Books | Angleterre | 653 |
| Oris | France | 2 |
| Orizons | France | 9 |
| Orphée | France | 6 |
| Orphée / La Différence | | 10 |
| Orphelya | France | 3 |
| Orphie | France | 48 |
| Orso | France | 11 |
| Ortho | France | 2 |
| Osaka | | 2 |
| Oscar Mondadori | Italie | 168 |
| Osismes Productions | | 1 |
| Oskar | France | 533 |
| Oskarson | France | 5 |
| Oskedith | France | 1 |
| Oslo | France | 16 |
| Osméosis | | 8 |
| Osmora | | 6 |
| Osolasba | | 1 |
| Ostraca | | 1 |
| Otava | France | 7 |
| Otema Autisme | France | 3 |
| Other Press | France | 12 |
| Otherlands | France | 37 |
| Ototo | France | 489 |
| Otrante | | 3 |
| Oû Pyid des Phares | France | 1 |
| Où sont les enfants ? | France | 2 |
| Ouest & Cie | France | 13 |
| Ouest-France | France | 549 |
| Ourania | France | 22 |
| Ouroboros | France | 2 |
| Ours et Loup | France | 1 |
| Ousia | Belgique | 1 |
| Outside | France | 2 |
| Outskirts Press | Etats-Unis | 3 |
| Outthink editing | Etats-Unis | 1 |
| Outworld | France | 4 |
| Ouverture | Suisse | 6 |
| Ouvrières | France | 11 |
| Ouvrir un Monde | France | 4 |
| Ovadia | France | 16 |
| Ovation Médias | France | 1 |
| Overfall Press | Etats-Unis | 1 |
| Overjoy | France | 3 |
| Overlap | Japon | 3 |
| Overlook | France | 5 |
| Overlook Press | France | 2 |
| Ovilorôi | | 2 |
| OVNI | | 3 |
| Oxbow | | 1 |
| Oxford University Press | Angleterre | 518 |
| Oxus | France | 8 |
| Oxygen Books | Angleterre | 1 |
| Oxymore | France | 44 |
| OXYMORON | France | 27 |
| Oz books | Etats-Unis | 1 |
| Ozark Mountain Publishing | Etats-Unis | 1 |
| Ozril | France | 3 |
| P&C | France | 1 |
| P&T | France | 7 |
| P'tit Baluchon | France | 4 |
| P'tit chou | Canada | 1 |
| P'tit Golem | France | 9 |
| P'tit Louis | France | 64 |
| P'tit loup | France | 1 |
| P'tite chose | | 1 |
| P. M. L | France | 2 |
| P.B. | France | 1 |
| P.O.L | France | 484 |
| P.R.N.G. | France | 1 |
| Paari | France | 1 |
| PAC | France | 12 |
| Pace press | Etats-Unis | 1 |
| Pacifica | | 1 |
| Packt | Etats-Unis | 3 |
| Padmakara | | 9 |
| pAf | France | 1 |
| Page à Page | France | 3 |
| Page après page | | 6 |
| Page Street | | 47 |
| Pages du Monde | France | 8 |
| Pages libres du Limousin | | 3 |
| Pages Ouvertes | | 13 |
| Páginas de Espuma | Espagne | 2 |
| Paidós | Espagne | 1 |
| Pain de mie | France | 2 |
