This course is an introduction to social movements from a sociological perspective. Social movements are collective, organized, and sustained vehicles for challenging authorities, power-holders and cultural institutions. Social movements are also one side of a broader category of "contentious politics" through which people demand and work for change in the social order. They come in many different forms, and they work on many different issues, yet they are always one key arenas for the articulation of social, political and personal alternatives to the status quo. In this class, we examine the origins, dynamics, and consequences of many different social movements. Along the way, we study why individuals join or leave movements, how movements are organized, and how movement organizations interact with broader environments. Although we draw upon a variety of case studies and theories, the emphasis will be on applying what we learn to understand the movements and movement organizations that you care about, and thereby - hopefully - to better understand the turbulent modern world in which we live.