Student movements are a distinctively modern phenomenon, emerging in societies that have a critical mass of students. While social conditions provide the base for student movements, political conditions are critical. They have usually emerged to challenge regimes that lack legitimacy or moral authority, in authoritarian states as well as in mature liberal democratic states. The critical conditions for the development of student movements are a moralistic grievance, an absence of effective opposition within the polity, and a lack of powerful allies. Students, relatively unconstrained by the obligations of adult life, may be the least inhibited opponents of morally compromised regimes, but alone they are seldom able to achieve their objectives. To succeed, student movements need to attract allies from reformists within governing elites or other sections of society. Student movements are common in modernizing societies under authoritarian regimes, but their development in fully democratic states is exceptional.