| Abbreviation | Definition |
|---|---|
| OPSF | Ogaden People Solidarity Forum |
| ORC | Orange River Colony |
| ORDP | Orange River Development Project, South Africa |
| ORSTOM | Office de la Recherche Scientifique et Technique d'Outre-Mer |
| OSIWA | Open Society Initiative for West Africa |
| OSIWA | Open Society Initiative for Western Africa |
| OSIWA | Open Society Institute for West Africa |
| OSPAAAL | Organization of Solidarity of African, Asian, and Latin American People |
| OSPAAL | Organization for the Solidarity of the Peoples of Asia, Africa and Latin America |
| OTM | Organização dos Trabalhadores de Moçambique |
| OUA | Organisation de l'Unité Africaine |
| OUPAC | Oxford University Pan African Conference |
| OUWA | Open University of West Africa |
| OVS | Oranje-VryStaat (Orange Free State) |
| OWWA | Organization of Women Writers of Africa |
| PA | Palm Avenue |
| PAAC | Partnership of African American Churches |
| PAAC | Preservation of African American Cemeteries |
| PAAN | Pan African Airlines Nigeria |
| PABIN | Pan Africa Bicycle Information Network |