This chapter focuses on transnational crimes. Though these were long part of the international criminal law (ICL) canon, it is only late in the discipline’s history that they became conceived as being something distinct. As such, while this chapter envisages the history of ICL, it also focuses more on the origin of the distinction in the Draft Code of Crimes Against the Peace and Security of Mankind. This distinction, which became quite influential, foregrounded crimes under general international law and crimes of international concern as two separate categories. However, this chapter takes a skeptical view of the distinction, noting the ‘question begging’ character of defining international crimes on the basis of an implicitly accepted notion of what international crimes are. But this is not to say that the attempt at drawing distinctions is fruitless—in fact, it sustains relevant conversations about, for example, the intrinsic character of gravity of various crimes in relation to each other. But, as this chapter shows, it does point to an irreducible element of faith in any act of prioritization.