Academic freedom is an unusual and complex set of norms and practices. It arises out of the combination of the corporate self-governance of medieval universities and the spirit of disciplinary scientific inquiry in modern research universities. It combines a principle of antiorthodoxy as to conclusions with the robust associational self-governance of scholarly communities whose members evaluate one another as participants in that shared enterprise. It has never been easily or wholly embraced by wider societies; today it is under wholesale attack. This article combines conceptual, normative, and historical analyses of academic freedom as a general norm with attention to conflicts over it in the mid-to-late 2010s and early 2020s. Some genuinely hard cases and questions tested the meaning of academic freedom and university values well before the current crisis.