This chapter gives an account of Weber’s concept of rationalization and how it has been used by subsequent social thinkers. The argument of the chapter is that rationalization is a central thread in Weber’s thought, and it explicates his ideas about how this process works in the realms of culture, the economy, and politics. It also discusses some thinkers who have made use of his ideas, including Ernest Gellner, Randall Collins, and Michael Mann. In Weber’s time, a major debate was about the rise and distinctiveness of the West. More recently, the debate has shifted to the causes and consequences of globalization. The final part of the chapter locates Weberian ideas about rationalization, and its limits, in this larger debate.