- Oasis – Association for Integrated Societies in Orissa
- OASIS – Onward Agency for Socio-Economic Integrated, Service, Kalhandi
- Oasis Charitable Trust, Delhi
- Oasis Foundation for Human and Natural Resource Development, Haveri
- Oasis Foundation, Dindigul
- Oasis Foundation, Guwahati
- Oasis Foundation, Oddanchatram
- Oasis India, Mumbai
- Oasis Institute of Health Sciences & Research Centre, Pune
- OASIS International Eunuch Welfare, West Godavari
- Oasis Social Welfare Society, Belgaum
- OASIS, Krishnagiri
- Oasys Society for Technology & Education Development, Neemuch
- Oazoane, Pudukkottai
- Ocean Bahuudeshiy Sanstha, Yavatmal
- Ocean Cadet Academy, Pune
- Ocean Ngo, Shimla
- Ocean Social Development Society, Pandhurna
- Ocean Technologies Society, Allahabad
- Oceanic Committee for Education Art & Nature, Rewa
- Ocfspir Samajik Sansthan, Laksar
- ODAM – Organisation of Development Action & Maintenance, Virudhunagar
- Odisha Institute For Social Development, Khurdha
- Odiyathur Nethaji Youth Club, Salem
- OFID – Organisation for Integrated Development, Purushottampur
- Oh Aa Ko Kho Shikshyatan, Howrah
- OIRC – International Organisation for Reduction of Catastrophes, New Delhi
- Ojasvini Seva Society, New Delhi
- Oju Welfare Association, Naharlagun
- Oleena Mahila Samajam, Calicut
- Oli Charitable Trust, Dharmapuri
- OLI Trust, Thiruvallur
- Olive Foundation, Pune
- Olive Orissa, Ganjam
- Oliyagam Trust, Madurai
- Om Bahuddeshiya Samajik Sanstha, Solapur
- Om Creations Trust, Mumbai
- Om Foundation, Noida
- Om Gurudev, Nasik
- Om Jai Ho Vishwatmaka Parivar, Pune
- Om Jai Shri Ram Sangh, Vidisha
- Om Kartikeya Maa Vindhyavasini Sewa Sanstha, Nasik
- Om Maa, Jajpur
- Om Mahila Audyogik Prashikshan Sansthan, Muzaffarpur
- Om Maruthi Vidya Sanstha, Bangalore
- Om Rajeshwar Multi-Purpose Society Trust, Osmanabad
- Om Rashtriya Janhit Sangthan, Delhi
- Om Sai Jansewa Society, Lucknow
- Om Sai Ram Educational Velfeyar society, Gonda
- Om Sai Ram Shiksha & Samaj Kalyan, Sagar
