This chapter explores philosophical contributions to international criminal law, focusing in particular on analyses of the concept of a crime against humanity and the justifiability of universal jurisdiction over those who commit such a crime.In what sense, if any, are crimes against humanity wrongs done to “humanity?”Does the label "crime against humanity" refer to a distinctive wrong committed by those who perform such acts?If not, what distinguishes crimes against humanity from other types of crime?The first half of this chapter critically examines several competing accounts of the concept of a crime against humanity and the answers they provide to these questions.The remainder of the chapter considers two approaches to justifying the international prosecution of crimes against humanity.The first grounds it in the dangers that such crimes pose to all human beings, while the second appeals to an (emerging) moral or political global community that makes perpetrators of crimes against humanity answerable to courts that act on behalf of all humanity.