Social movements are a type of contentious politics, rational, sensible politics by non-electoral means; and thus, related to social change and to the res publica—public affairs, understood as the issues affecting members of a polity. They may also include the use of violence or culturally recognizable non-routine displays of public discontent: e.g., marches, strikes. This chapter reviews common theoretical and methodological approaches to social movement analysis and introduces the case studies in the second part of the book, which examine contemporary movements in relation to Charles Tilly’s research model.