- Open Society Institute for West Africa
- Open Society Justice Initiative
- Opera Mundi
- OperaMundi | BdF
- OperaMundi | Brasil de Fato
- Ophélie Latil et Aurélie Chatelard
- Organisation mondiale contre la torture
- Organizações Moçambicanas da Sociedade Civil | @Verdade
- Orlando Castro
- Orlando Patterson
- Oru Ntui
- Orwa Michael
- Osai Justina Ojigho
- Osai Ojigho
- Osarhieme George
- Osaze Lanre Nosaze
- Oscar D. Simela
- Oscar Fortin
- Oscar H. Blayton
- Oscar Ramjeet
- OSI Angola, AJPD
- Osita Ebiem
- Osiwa
- Osman D. Osman
- Osman Naway
- Osman Nawy
- Ota Benga Alliance
- Otiato Guguyu
- Otieno Orwa
- Otim Denis Barnabas