Sir James Mirrlees, co‐recipient of the 1996 Nobel Memorial Prize in Economic Sciences, passed away in August 2018. This article outlines how his work has transformed economists’ understanding of their discipline – from the principles of tax design to the theory of contracts and beyond. By conceiving of policy questions in terms of information asymmetries between governments and taxpayers, Mirrlees demonstrated how to conduct convincing analysis of redistributive objectives together with incentive effects in the design of general tax systems and public policy more broadly. His ability to simplify complex problems in ways that reveal their tractable essence means that his work has yielded insights that have reverberated throughout the discipline. It has also proved highly fruitful for practical policy design.