Elinor and Vincent Ostrom spent their careers working in fields outside third-sector studies, yet a significant body of their work has important implications for nonprofit organizations and the wider third sector. From their academic base at the Workshop on Political Theory and Policy Analysis at Indiana University, they built a large body of research and theory on a broad range of topics that bear on nonprofit and voluntary action theory, including self-governance, collaboration, coproduction, polycentrism, federalism, and numerous others. This article examines and critiques selected aspects of their role in the vast international network of commons studies and projects, including a body of my own work stretching back several decades on the commons theory of voluntary action (CTVA). Recent work on new commons, information commons, and knowledge commons points toward a convergence of the Ostrom’s work on commons with commons research and theory in our field.