The Mishnah is the foundational document of rabbinic Judaism--all of rabbinic law, from ancient to modern times, is based on the Talmud, and the Talmud, in turn, is based on the Mishnah. But the Mishnah is also an elusive document; its sources and setting are obscure, as are its genre and purpose. In January 2021 the Harvard Center for Jewish Studies and the Julis-Rabinowitz Program on Jewish and Israeli Law of the Harvard Law School co-sponsored a conference devoted to the simple yet complicated question: "What is the Mishnah?" Leading scholars from the United States, Europe, and Israel assessed the state of the art in Mishnah studies; and the papers delivered at that conference form the basis of this collection. Learned yet accessible, What Is the Mishnah? gives readers a clear sense of current and future direction of Mishnah studies.