Grapevines
- Oakland County Women for Good
- Oakland Guys for Good
- Oakland Stock
- Oakland Women for Good
- Oasis House for Healing and Restoration (Domestic Violence organization)
- Occidental College Alumni Giving Circle
- OC Women for Good Giving Circle
- OFJCC Chai Giving Circle
- Ohio Women for Blue States
- Ojai Women’s Fund
- OJCF Giving Council
- Oklahoma City Business Leaders for Good
- Oklahoma City Next-Gen Women for Good
- Oklahoma Native Assets Coalition: Serving Native Communities Across the U.S.
- Olim Making Change
- Olive Branch Giving Circles
- Olympia Community Solar
- Omaha Professional Women for Good
- Omaha Venture Group
- Omar's Giving Circle
- Omicron Sigma Zeta Foundation
- One Hand Up
- One Percent for Moms
- One Sky Giving Circle
- One State at a Time
- Open Hearts, Open Purses
- Operation CatSnip of Kentucky, Inc
- Orange County Latino Giving Circle
- Orange County Women’s Giving Circle
- Orange is the New Blue
- Orchid Giving Circle
- Ordinary Folks Fight for Democracy!
- Oregon Jewish Community Foundation Giving Council
- Orit Blatt's Giving Circle
- Orlando Women for Good
- Ottawakent Women Who Care
- Ouray County Giving Girls
- Our Children Deserve Better
- Our Glass
- Our Michigan
- Our saharienne women
- Our Sarasota Fund
- Our soldier’s
- Our Strategic Giving Circle: Leveraging Power in State Legislatures
- OUT Fund
- Outgiving Circle
- Overland Park Professional Women for Good
- Overton Oversubscribe Giving Circle
- Oxfam-Asian Circle
- Oxnard Professional Women for Good
- Oxygen
- Oy vey, it's not okay
- OY VEY THINGS ARE NOT OK!