Since the fifteenth century, scholars have wondered about the authorship of the anonymous series of papal biographies from St. Peter onwards, now known as the Liber pontificalis. Bartolomeo Platina (ca. 1421–81) and Onofrio Panvinio (1530–68) were responsible for the false notion that “Anastasius the Librarian” was the book’s principal author. This article reconsiders why the myth of Anastasius was created and how it was passed on. It rejects the thesis by Girolamo Arnaldi that Platina created this myth on purpose, with the intention of furthering his own career. Rather, Platina produced the myth more or less accidentally. Yet this myth proved so powerful that it was not completely dispelled until the late nineteenth century.