What do economists do in central banks? Why do central banks hire economists? This Element investigates the evolving role of economists and economic knowledge within central banks, arguing that their current centrality is neither self-evident nor historically inevitable. It shows that the influence of economists within central banks is the result of a complex, gradual, and uneven historical process shaped by institutional structures, disciplinary transformations, and shifting relationships between science and policy. Drawing on a rich but dispersed body of literature, the Element traces how economists progressively gained authority through the establishment of statistics departments, the adoption of macroeconometric models, and the emergence of a shared cognitive infrastructure between academia and central banks. Rather than focusing on individuals or doctrines, it examines general trends and institutional shifts across national case studies to show how central banks function as boundary organizations, at the intersection of science and policy.