This chapter examines Jürgen Habermas's major contributions to social and political thought. Habermas is regarded as one of the most influential figures in contemporary political theory. In his later work Habermas has begun to expand the normative political implications of his work in social theory and philosophy, culminating in Between Facts and Norms. This chapter first provides an overview of Habermas's earlier work, especially his study on the transformation of the liberal or bourgeois public sphere, before discussing his theory of communicative action (or action based on mutually supposed validity claims). It then considers Habermas's attempt, in Between Facts and Norms, to develop an account of deliberative politics anchored on the idea of political legitimacy and concludes with an analysis of cosmopolitanism as well as his views on discourse theory, democracy, the system of rights, and ‘weak’ and ‘strong’ publics.