- Open Mind Tanzania
- OpenSasa
- organisation for child, youth and women empowerment support
- ORGANIZATION FOR LAND AND AGRICULTURE IMPROVEMENT
- Organization for Rural Self-Help Initiatives
- Organization for Vulnerable group Assistance
- Organization of People Empowerment (OPE)
- ORGANIZATION OF SPECIAL NEEDS EDUCATION TEACHERS
- Orkonerei Mass Media
- ORPHANS AND STREET CHILDREN ORGANIZATION