William Foster

William Foster is a partner in Bridgespan’s Boston office and the firm’s managing partner. He is an active thought leader on issues of philanthropy and social change.

Since joining the firm in 2002, William has supported the success of some of the sector’s most innovative philanthropies (e.g., Blue Meridian Partners, Co-Impact, TED Audacious) and some of the highest impact nonprofits (e.g., Youth Villages and Anti-Defamation League). He has a particular focus on the diligence, structuring, and supports required for philanthropic “big bets” and strong funding models for nonprofits.

William spent eight years as the head of Bridgespan's U.S. advisory services, working closely with Bridgespan’s partners to guide the overall consulting practice. During this time, William worked with leaders across the firm to evolve Bridgespan's services for philanthropies and nonprofits, to deepen Bridgespan's commitment to equity, and to expand Bridgespan significantly.

Based on his clients’ experiences, William has dedicated himself to research on the topics of philanthropic "big bets" and nonprofit funding models. He recently published "Policy Incrementalism and How Philanthropy's Support Can Turn Small Sustained Steps into Big Impact" (Bridgespan.org, 2024), “Endow Black-Led Nonprofits” (Stanford Social Innovation Review, 2021). Other publications include: “Becoming Big Bettable” (Stanford Social Innovation Review, 2019), “Making Big Bets for Social Change” (Stanford Social Innovation Review, 2015), “When You’ve Made Enough to Make a Difference” (Harvard Business Review, 2011), “Ten Nonprofit Funding Models” (Stanford Social Innovation Review, 2009), “How Nonprofits Get Really Big” (Stanford Social Innovation Review, 2007), and “Should Nonprofits Seek Profits?” (Harvard Business Review, 2005).

William has served as the executive director of the Jacobson Family Foundation (now known as One8), an outcomes-oriented funder making grants to support educational excellence, equality, and Jewish continuity in the United States and Israel.

Prior to joining Bridgespan, William worked at Bain & Co. He received his BA from Harvard College and his MBA from Stanford University where he was an Arjay Miller Scholar. William serves on the board of Phare Bio and chairs the board of Gann Academy.  He lives outside of Boston with his wife Rachel and their four wonderful children.