- Organate for the Nation’s Advantages by a Mission, New Delhi
- Organisation for Community Development, Kanyakumari
- Organisation for Development Action, Trichirapally
- Organisation for Development, Integrated, Social & Health Action, Ganjam
- Organisation for Integrated Development, Ganjam
- Organisation for Native Women Aid & Rural Development, Kolkata
- Organisation for Responsible & Community-Based Tourism, New Delhi
- Organisation for Rural Education, Tiruvannamalai
- Organisation for Rural Reconstruction & Social Service Action, Nayagarh
- Organisation for Rural Survival, Belonia
- Organisation for Social Change & Rural Development, Bhubaneshwar
- Organisation for Social Help & Research Evolution, Jabalpur
- Organisation for Welfare to Society, Bhubaneswar
- Organisation of Womens Network, Maheshtala
- Organization for Developmental Activities, Ranchi
- Organization for Go Green Initiative, Guwahati
- Organization for Poor and Economical Needs (Open), Secunderabad
- Organon Technology, Mau
- Oriental Human Rights Protection Forum, Thane
- Orissa Educational & Cultural Trust, Keonjhar
- Orissa Institute Of Film, Television & Theatre, Khordha
- Orissa Khet Mazdoor Kishan Parisad, Baripada
- Orissa Mahila Vikash Samiti, Jajpur
- Orissa Pardesh Adivasi Vikash Parishad, Kalahandi
- Orissa Patita Udhar Samiti, Bhubaneswar
- Orissa Professional Development Service Consultants, Rayagada
- Orissa Rural & Tribal Development Society, Khurda
- Orissa Social Service Institute, Cuttack
- Orissa Voluntary Health Association, Bhubaneshwar
- Orkids Foundation, New Delhi
- ORRA – Orissa Rural Reconstruction Association, Bhubaneswar
- ORRISSA – Organisation for Rural Reconstruction & Integrated Social Service Activities, Bhubaneswar
- ORRM – Orgnisation for Rural Reconstruction Movement, Anantapur
- ORUPA, Bhubaneswar
- Osca Youth, Delhi
- Oscare Foundation and Research, Madurai
- Oseous Welfare Society, Jhansi
- OSJS – Om Sai Jansewa Society, Lucknow
- Ouicare, Puducherry
- OUPS – Organization for Under Privileged Society, Kolkata
- Our Ambition Patpat Ganj Village, East Delhi
- Our Helpinghand, Delhi
- Our Hope Welfare Society, Bhopal
- Our Ladys Educational Society, Satara
- Our Life Vision, Visakhapatnam
- Outreach Association Of Volunteers For Rural Development, Bangalore
- OUTREACH, Hyderabad
- Overcheri Rethinam Sengammal Educational Trust, Chennai
- Overseas Hindu Royal Society, Trivandrum
- Oxfam (I) Trust, Secunderabad