How have exchanges shaped financialization? This chapter argues that similar to other financial market actors, securities exchanges have themselves undergone a significant transformation. In the last 25 years, marketization, internationalization, and digitization have fundamentally changed the way exchanges function, turning them from national marketplaces into markets actors. As a result of this transformation, exchanges have become crucial agents in processes of financialization. First, by organizing capital markets they influence market dynamics, facilitating volatility and market stability. Second, exchanges have turned into agents of disintermediation, selling and exporting financial technologies and expertise, facilitating the development of capital markets globally. Third, exchanges have emerged as politically and economically powerful players, both vis-à-vis other market actors but also towards regulators and states. Overall, through their transformation exchanges have become crucial actors in the spreading of capital markets, the transformations of contemporary finance and the politics of financialization.