A definitive interpretation of academic freedom as a First Amendment right, drawing on a comprehensive survey of legal cases. Is academic freedom a First Amendment right? Many think so, yet its relationship to free speech as guaranteed by the Constitution is anything but straightforward. David Rabban examines the extensive case law addressing academic freedom and free speech at American universities, developing a robust theory of academic freedom as a distinctive subset of First Amendment law. In subsuming academic freedom under the First Amendment, Rabban emphasizes the societal value of the contribution to knowledge made by the expert speech of professors, the classic justification for academic freedom in the influential 1915 Declaration of the American Association of University Professors (AAUP). Any indication that professors might be disciplined because people without academic training disagree with their scholarly views would undermine confidence in the integrity of their work and therefore their ability to perform this vital function on behalf of the public. Rabban argues that academic freedom fosters two central First Amendment values recognized by courts in a wide range of contexts: the production and dissemination of knowledge and the contribution of free expression to democratic citizenship. The First Amendment right of academic freedom applies most directly to professors, but it also plausibly extends to the educational decisions of universities and to students' learning interests. More broadly, this vision of academic freedom can guide in developing additional distinctive First Amendment rights to protect the expert expression of journalists, librarians, museum curators, and other professionals. At a time when academic freedom is under attack from many directions, Academic Freedom proposes a theoretically satisfying and practically useful guide to its meaning as a First Amendment right.