Foundations are traditionally viewed as civic-minded but politically neutral organizations. Yet foundations, if they choose, can become involved in a wide variety of activities aimed at influencing public policy. Here we lay out the rationale for thinking about foundations as interest groups in the American political system. There are differences between conventional interest groups and foundations to be sure, but there are similarities as well. The choices foundations make as to whether to consciously try to influence government appears to be guided by organizational norms, regulatory requirements, and the beliefs of boards, donors, and internal leadership.