The William and Flora Hewlett Foundation is a private, nonpartisan foundation established in 1966 by Hewlett-Packard co-founder William R. Hewlett and his wife, Flora Lamson Hewlett. The foundation supports creative thinkers and problem solvers working to build a more inclusive society where people, communities and the planet can flourish. Its grantmaking covers areas including education, climate and the environment, gender equity and governance, U.S. democracy, racial justice, the performing arts, effective philanthropy and economic policy.

Based in the San Francisco Bay Area, the foundation provides grants to organizations ranging from community-based nonprofits and artists to universities, research institutions and policy organizations. It emphasizes long-term partnerships, flexible funding, and collaboration, with work spanning the United States and other regions including Africa and Latin America. In 2024, the foundation awarded $631 million in grants and had approximately $13.9 billion in assets. Amber D. Miller, an astrophysicist and university leader, has served as president since September 2024.