| O L Halsell Foundation | $5M | 211 | $15K |
| The O Wayne Rollins Foundation C/o Rfa Management Co LLC | $39.5M | 29 | $2K |
| The O-i Charities Foundation | $1.4M | 187 | $600 |
| The O'brien Family Foundation | $1.5M | 107 | $5K |
| O'connell Family Foundation Inc C/o Daniel S O'connell | $1.6M | 15 | $5K |
| The O'connor & Hewitt Foundation | $4.1M | 155 | $10K |
| O'donnell Family Charitable Trust Joseph Matzkin Esq Trustee | $1M | 7 | $5K |
| O'donnell Foundation | $218.8M | 43 | $1M |
| O'loughlin Family Foundation | $2.7M | 7 | $15K |
| The O'neil Family Foundation Inc | $3.6M | 118 | $12K |
| O'Neill Family Charitable Foundation | $1.5M | 11 | $15K |
| O'neill Family Charitable Trust | $8.5M | 149 | $20K |
| O'scannlain Family Charitable Foundation | $1.8M | 21 | $25K |
| The Oak Foundation USA C/o Kemnay Advisory Services Inc | $14.3M | 16 | $400.8K |
| The Oak Hill Fund | $2.2M | 73 | $10K |
| Oak Ridge Foundation | $2.8M | 14 | $1K |
| Oakhill Foundation | $3.3M | 8 | $194K |
| Oakland Family Foundation | $1.1M | 31 | $25K |
| The Oaklawn Foundationinc | $2.1M | 117 | $20K |
| Oakwood Foundation Charitable Trust | $6.9M | 46 | $10K |
| Oarsmen Foundation | $2.9M | 77 | $20K |
| Oates Family Foundation | $1.7M | 27 | $5K |
| Oatey Foundation | $1.3M | 56 | $10K |
| Oberkotter Foundation | $6.3M | 17 | $154.4K |
| Oberndorf Family Foundation | $36M | 112 | $25K |
| Oberweiler Foundation | $1.7M | 104 | $15K |
| Obici Healthcare Foundation Inc | $5.2M | 118 | $4K |
| Oceanfirst Foundation | $3.1M | 1,087 | $1.1K |
| Oceanic Heritage Foundation C/o Morgan Stanley | $2.4M | 78 | $15K |
| Ochylski Family Foundation | $1.7M | 14 | $90K |
| Ocie V Miller Memorial Foundation Inc | $1.3M | 11 | $100K |
| Oclo Inc | $2.3M | 13 | $85K |
| Ocora Foundation | $1M | 16 | $77.5K |
| October Mountain Foundation Inc | $9.4M | 141 | $30K |
| Odell Rs & Hp Fund Tua-main | $5.1M | 118 | $30K |
| Odyssey Group Foundation | $2.8M | 16 | $75K |
| Oechsle Family Foundation Inc | $6M | 92 | $50K |
| Offerdahl Family Foundation | $1.8M | 89 | $3K |
| Offutt Family Foundation | $9.6M | 114 | $5K |
| Ogc Charitable Foundation | $1.5M | 18 | $67.6K |
| Oge Energy Corp Foundation Inc | $4.3M | 86 | $10K |
| Ohel Harav Yehoshua Boruch Foundation Inc | $2.4M | 9 | $50K |
| Ohel Naftoly | $1.7M | 76 | $2.7K |
| Ohio National Foundation | $1M | 6 | $10.7K |
| The Ohnell Family Foundation | $4.1M | 82 | $10K |
| The Oki Foundation | $2.2M | 63 | $10K |
| Olander Family Foundation Inc | $1M | 204 | $4K |
| Old Ladies Home Association | $3.2M | 15 | $63.5K |
| The Old Oak Foundation | $1M | 21 | $25K |
| Oldham Little Church Foundation | $1.7M | 129 | $14K |
| Oleson Foundation | $4.7M | 230 | $11.1K |
| Olive B Cole Foundation Inc | $1.3M | 63 | $10K |
| Oliver & Cunningham Fam Fdn-main | $1.2M | 50 | $12.5K |
| Oliver & Jennie Donaldson Char(1071 | $1.8M | 36 | $26K |
| Oliver Charitable Corporation | $1.3M | 13 | $50K |
| Oliver Dewey Marcks Foundation | $1M | 68 | $10K |
| The Oliver Family Foundation C/o Richard D Oliver | $5.2M | 120 | $11.3K |
| The Olseth Foundation | $1.8M | 102 | $10K |
| Olson Family Foundation Inc | $4.4M | 128 | $25K |
| Olsson Foundation Inc | $1.3M | 54 | $2.5K |
| Oluv C Joynor Foundation Inc | $1.5M | 55 | $15K |
| Omidyar Network Fund Inc | $38.1M | 242 | $100K |
| On Semiconductor Foundation | $2.6M | 6 | $12.5K |
| The Once Here Foundation | $2.8M | 14 | $137.5K |
| Once Upon A Time Foundation | $10.7M | 1,039 | $350 |
| The Onda Foundation Inc | $3M | 98 | $20.3K |
| One Accord Charity Foundation | $1.6M | 20 | $53.8K |
| One Earth Future Foundation Inc | $1.2M | 5 | $5K |
| One Gas Foundation Inc | $2.6M | 212 | $2.4K |
| One Hive Foundation | $2.3M | 74 | $2K |
| One Life Foundation Inc | $2.3M | 5 | $218.8K |
| One World Fund | $1.7M | 73 | $19.5K |
| One8 Foundation | $48.8M | 188 | $50K |
| OneAmerica Foundation Inc | $1M | 68 | $8K |
| Oneok Foundation Inc | $3.7M | 204 | $4.9K |
| Oneroot Foundation | $15.1M | 104 | $25K |
| Onesight Essilorluxottica Foundation Fund | $10.3M | 79 | $27.7K |
| Onion Foundation | $4.4M | 245 | $15K |
| Ono Pharma Foundation | $6.2M | 24 | $258.8K |
| Op & We Edwards Foundation Inc | $1.6M | 63 | $20K |
| Open Doors International Inc | $22.6M | 9 | $611.7K |
| Open Horizon | $2.4M | 83 | $18.4K |
| Open Minds Align Foundation Inc | $1.1M | 74 | $4K |
| Open Society Institute | $146.9M | 559 | $15K |
| Open Stewardship Foundation | $1.2M | 169 | $5K |
| Opera House Fund Inc C/o Doug Dean | $1.2M | 26 | $28K |
| Oppenheim Family Fund Inc | $1.3M | 181 | $2.5K |
| Oppenheimer&haas Xxxxx1004 | $2.4M | 27 | $70K |
| Oppenstein Brothers Foundation | $3.6M | 236 | $15K |
| The Opportunity Foundation | $1M | 8 | $100.5K |
| Opportunity Foundation | $2.4M | 156 | $15K |
| The Oprah Winfrey Charitable Foundation | $23.4M | 25 | $150K |
| Opus Foundation | $5.5M | 164 | $10K |
| Opus Prize Foundation C/O Adler Trust Company | $1.4M | 14 | $10K |
| Oracle Education Foundation | $1.1M | 8 | $15K |
| Orange Crimson Foundation | $6.5M | 5 | $1M |
| The Orchard Farm Foundation | $2M | 51 | $10K |
| The Orchard Foundation C/o Heidi Lehner Corient Private Wealth | $3.1M | 168 | $5K |
| The Orchard House Foundation -A Nevada Non Profit Corporation | $1.2M | 54 | $20K |
| Ordean Foundation | $1.5M | 50 | $20K |
| OReilly Automotive Foundation Inc | $2.5M | 87 | $20K |
| Orentreich Family Foundation | $1.2M | 85 | $4.6K |
| The Organix Foundation | $5.1M | 7 | $7.3K |
| Orin Smith Family Foundation | $1.4M | 12 | $25K |
| Orion & Emma B Hurlbut Tr Fbo Memorial Fd | $1.2M | 7 | $150K |
| Orland Bethel Family Foundation | $27.8M | 10 | $7.5K |
| Ormjmp Foundation | $3.3M | 19 | $125K |
| Oro Y Plata Foundation | $1.8M | 84 | $25K |
| The Orokawa Foundation Inc C/o Martin J Eby | $11.1M | 115 | $50K |
| The Oros Foundation | $1.4M | 8 | $125K |
| Orosz Family Foundation Inc | $1.7M | 27 | $25K |
| Orr Family Foundation | $2.2M | 28 | $50K |
| The Orr Family Foundation | $1.8M | 14 | $70K |
| Orris C&b Dewey Hirtzel Memorial Fd | $1.3M | 52 | $7.5K |
| Orsa Foundation | $1M | 93 | $8K |
| Orscheln Industries Foundation Inc | $6M | 552 | $1K |
| Orthodox Vision Foundation | $2.2M | 47 | $5K |
| The Ortner Family Foundation | $2.2M | 18 | $93.6K |
| Osaic Foundation Inc | $1.1M | 281 | $1K |
| Oscar J Tolmas Charitable Trust | $2.9M | 74 | $20.9K |
| The Oscar Rennebohm Foundation Inc | $6.3M | 73 | $75K |
| Oscar T and Olivann Hokold Foundation | $2.8M | 31 | $50K |
| OShea Family Foundation | $1.1M | 30 | $10K |
| Oshkosh Corporation Foundation Inc | $2.4M | 133 | $6.5K |
| Osilas Foundation | $3.3M | 75 | $10K |
| The Osprey Foundation Inc | $6.1M | 27 | $150K |
| Ossen Family Foundation | $1.5M | 132 | $2.2K |
| Osteopathic Heritage Foundation | $12.6M | 64 | $40.5K |
| Osullivan Foundation Trust Dtd 122299 | $3.6M | 13 | $40K |
| Otha H Grimes Foundation | $2.3M | 8 | $287.5K |
| The Otho Sa Sprague Memorial Institute | $4.4M | 35 | $100K |
| Otis & Bettina Chandler Foundation | $2.4M | 26 | $37.5K |
| The Otis Booth Foundation | $14.4M | 140 | $25K |
| Otter Tail Corporation Foundation | $1.1M | 119 | $5K |
| Otter Tail Power Company Foundation | $1.7M | 389 | $1.2K |
| Otto & Edna Neely Foundation | $1M | 60 | $10K |
| Otto Bremer Trust | $125.8M | 1,063 | $55K |
| The Otto M Budig Family Foundation | $1.1M | 15 | $25K |
| Otto Schoitz Foundation | $7.2M | 108 | $25K |
| The Ottosen Family Foundation | $1.7M | 29 | $48.1K |
| Ottumwa Regional Legacy Foundation Inc | $3.1M | 216 | $1.1K |
| Otzar Hachesed Foundation Trust | $1.2M | 64 | $9.1K |
| Our Home Ukraine Foundation | $1.3M | 7 | $174K |
| Our Little Light Foundation | $1.2M | 41 | $20K |
| Ousri Foundation for Goodwill | $3.6M | 10 | $3.8K |
| Outcalt Foundation | $1.6M | 37 | $5K |
| Outrageous Foundation Inc C/o Robert Mcgrath | $2.7M | 81 | $30K |
| Outride fka The Specialized Foundation | $1.2M | 103 | $12.4K |
| The Overbrook Foundation | $8.3M | 160 | $47.5K |
| Overlake Foundation Inc | $1.1M | 56 | $6K |
| The Owens Family Foundation | $4.6M | 17 | $100K |
| The Owsley Brown III Philanthropic Found | $2.7M | 95 | $10K |
| The Oxford League Inc | $1.7M | 11 | $25K |
| The Oxley Foundation | $1M | 7 | $50K |
| Ozuah Family Foundation Inc Philip Ozuah Director | $1M | 14 | $39.7K |