| Name | Type | Country | Number |
|---|---|---|---|
| Ōda Shubban太田出版 | Editor | Japan | 2 |
| Ofelbe | Editor | France | 10 |
| Omaké Books | Editor | France | 5 |
| Omaké manga | Imprint | France | 3 |
| Operaオペラ | Magazine | Japan | 1 |
| Otome Kōshin乙女通信 | Magazine | Japan | 1 |
| Ototo | Editor | France | 44 |
| OVERLAPオーバーラップ | Editor | Japan | 1 |
| OVERLAP bunkoオーバーラップ文庫 | Imprint | Japan | 1 |