Public participation is well known for its practitioner insights and wealth of case reports. This knowledge is essential and has been well employed. Likewise, the theoretical literature on public participation is growing rapidly. The need for better conceptual and theoretical understandings of public participation has become clear. Public participation theories have not received great attention, and few have been proposed or tested. Yet theory offers much to practitioners of various interventions. The authors summarize work toward developing a public participation theory and propose a way to conceptualize its skeletal components. The authors recognize that any theory must acknowledge that different people have different beliefs about what public participation should accomplish. Further, contextual variables affect a process’s character and outcomes. The authors begin with a discussion of theory’s importance to scholars, practitioners, and participants and provide an overview of existing approaches. The authors present findings from two empirical case studies used to further develop their theory of fair and competent public participation. They conclude with some observations about challenges and ways forward.