Formerly in the possession of Harold Willoughby, professor of early Christian origins at the University of Chicago, this unpublished fragment of the Gospel of John in Greek created a stir when it appeared briefly on a well-known auction site in January 2015. Having obtained permission from the owner to edit and publish the manuscript, I offer in this article the results of my analysis of the so-called Willoughby Papyrus, which I have assigned to the third or fourth century. On the basis of new images of the fragment, I provide a transcription of the text, discuss its apparent bookroll format, and assess its text-critical value. Finally, I present the secondary text on the verso and offer some tentative suggestions about its literary character. Though no more than six fragmentary lines survive on either side, the Willoughby Papyrus is of historical interest for three reasons: (1) it is a rare example of a New Testament fragment in which "God" is not abbreviated as a nomen sacrum, a "sacred name"; (2) it furnishes scholars with the first defensible example of a New Testament text written on the front side of an unused bookroll; and (3) it preserves six lines from an otherwise unknown Christian literary text. The Willoughby Papyrus has the potential to provide fresh insight into the emergence and standardization of nomina sacra conventions, the transition from the bookroll to the codex, and the circulation of canonical and noncanonical Christian writings.