Strategic planning has become a fairly routine and common practice at all levels of government in the United States and elsewhere. It can be part of the broader practice of strategic management that links planning with implementation. Strategic planning can be applied to organizations, collaborations, functions (e.g., transportation or health), and to places ranging from local to national to transnational. Research results are somewhat mixed, but they generally show a positive relationship between strategic planning and improved organizational performance. Much has been learned about public-sector strategic planning over the past several decades but there is much that is not known. There are a variety of approaches to strategic planning. Some are comprehensive process-oriented approaches (i.e., public-sector variants of the Harvard Policy Model, logical incrementalism, stakeholder management, and strategic management systems). Others are more narrowly focused process approaches that are in effect strategies (i.e., strategic negotiations, strategic issues management, and strategic planning as a framework for innovation). Finally, there are content-oriented approaches (i.e., portfolio analyses and competitive forces analysis). The research on public-sector strategic planning has pursued a number of themes. The first concerns what strategic planning “is” theoretically and practically. The approaches mentioned above may be thought of as generic—their ostensive aspect—but they must be applied contingently and sensitively in practice—their performative aspect. Scholars vary in whether they conceptualize strategic planning in a generic or performative way. A second theme concerns attempts to understand whether and how strategic planning “works.” Not surprisingly, how strategic planning is conceptualized and operationalized affects the answers. A third theme focuses on outcomes of strategic planning. The outcomes studied typically have been performance-related, such as efficiency and effectiveness, but some studies focus on intermediate outcomes, such as participation and learning, and a small number focus on a broader range of public values, such as transparency or equity. A final theme looks at what contributes to strategic planning success. Factors related to success include effective leadership, organizational capacity and resources, and participation, among others. A substantial research agenda remains. Public-sector strategic planning is not a single thing, but many things, and can be conceptualized in a variety of ways. Useful findings have come from each of these different conceptualizations through use of a variety of methodologies. This more open approach to research should continue. Given the increasing ubiquity of strategic planning across the globe, the additional insights this research approach can yield into exactly what works best, in which situations, and why, is likely to be helpful for advancing public purposes.