In this paper, I offer a prolegomenon to the philosophy of harm reduction. I begin with an overview of the philosophical literature on both harm and harm reduction, and a brief summary of harm reduction scholarship outside of philosophy in order to make the case that philosophers have something to contribute to understanding harm reduction, and moreover that engagement with harm reduction would improve philosophical scholarship. I then proceed to survey and assess the nascent and still modest philosophy of harm (...) reduction literature that has begun to emerge. I pay particular attention to two Canadian philosophers who have called for the expansion of harm reduction beyond the realm of so-called “vice”. Finally, I sketch some of the most interesting and important philosophical issues that I think the philosophy of harm reduction must grapple with going forward. (shrink)