| Name ▲ | Type | CR | Version | Book |
|---|---|---|---|---|
| Obzedat Ghost | Undead | 8 | 2014 | Guildmasters' Guide to Ravnica |
| Occult Extollant | Humanoid | 6 | 2014 | Critical Role: Call of the Netherdeep |
| Occult Initiate | Humanoid | 2 | 2014 | Critical Role: Call of the Netherdeep |
| Occult Silvertongue | Humanoid | 8 | 2014 | Critical Role: Call of the Netherdeep |
| Oceanus | Humanoid | 1/2 | 2014 | Ghosts of Saltmarsh |
| Ochre Jelly | Ooze | 2 | 2014/2024 | Multiple Books (MM, XMM) |
| Octon Modron | Construct | 11 | 2014 | Morte's Planar Parade |
| Octopus | Beast | 0 | 2014/2024 | Multiple Books (MM, XMM) |
| Oculorb | Aberration | 9 | 2014 | Phandelver and Below: The Shattered Obelisk |
| Oddlewin | Fey | 2 | 2014 | The Book of Many Things |