O
| Publisher | Website | ISBN prefix |
| Ocean Press
Ocean Sur |
www.oceanbooks.com.au | 1-875284, 1-876175, 1-920888, 1-921235
1-920888, 1-921235, 1-921438 |
| Old Street Publishing | www.oldstreetpublishing.co.uk | 1-905847 |
| Open Court | www.opencourtbooks.com | 0-8126, 0-87548, 0-89385, 0-914417 |
| Oro editions | www.oroeditions.com | 0-9814628, 0-9820607, 0-9793801, 0-9795395 |
| Osho Media | 0-9818341 | |
| Owners Manual Press | www.ownersmanual.com | 0-9744521 |
P
| Publisher | Website | ISBN prefix |
| Palace Publishing Group, LP | www.palacepress.com | 1-60109, 1-932771 |
| Papaloa Press | www.explorekauai.com | 0-9615498, 0-9745956 |
| Parallax Press | www.parallax.org | 0-938077, 1-888375 |
| Paris Press | www.parispress.org | 0-9638183, 1-930464 |
| Passporter Travel Press | www.passporter.com | 1-58771 |
| Paul Dry Books | pauldrybooks.com | 0-9664913, 0-9679675, 0-9793787, 1-58988 |
| PC Treasures, Show Me How | 1-60072, 1-84764 | |
| Pear Press | www.pearpress.com | 0-9797777 |
| Pearson Venture Group | 0-9743552 | |
| Persephone Books | www.persephonebooks.co.uk/books | 1-906462 |
| Personify Press | www.personifypress.us | 0-9797491 |
| Plain White Press | www.plainwhitepress.com | 0-9777383, 0-9815004 |
| Plexus Publishing | www.plexusbooks.com | 0-85965, 0-906008 |
| Plum Blossom Books | www.parallax.org | 1-888375 |
| Pomegranate Press | www.pompress.com | 0-938817 |
| Pond Press | www.pondpress.com | 0-9666776, 0-9761955 |
| powerHouse Books | www.powerhousebooks.com | 1-57687, 1-890451, 0-9651042, 3-89904, 0-9761416, 0-9798110, 3-937946, 0-940642, 3-926318 |
| Process
Daniel 13 / Process Dilettante |
processmediainc.com.com | 0-9760822, 1-934170
0-9760822, 1-934170 0-9664272 |
| Profile Books | www.profilebooks.com | 1-84668, 1-86197 |
| Public Affairs Books | www.publicaffairsbooks.com | 1-58648, 1-891620 |
| Purple Bear Books | www.purplebearbooks.com | 1-933327 |
| PVG | 0-9762686 |