- Old Nguvumali Women Centre
- One World One Love Foundation
- Open Mind Tanzania
- ORGANIZATION FOR LAND AND AGRICULTURE IMPROVEMENT
- Organization for Rural Self-Help Initiatives
- Organization for Vulnerable group Assistance
- Organization of People Empowerment (OPE)
- Orkonerei Mass Media
- PAMOJA ENTREPRENEURSHIP SUPPORT FOR COMMUNITY DEVELOPMENT (PESCODE)
- PANGANI COAST CULTURAL TOURISM PROGRAMME