This chapter discusses the law of war crimes. It begins by introducing the basic principles of the law of armed conflict (LOAC): distinction and proportionality. It then distinguishes between international and non-international armed conflicts; outlines the contextual element and mental element required for war crimes; provides an overview of the prohibited acts that may form the conduct underlying a war crime; and examines select war crimes in more detail. The chapter concludes with a table comparing the range of offences applicable under the International Criminal Court (ICC) Statute to NIACs and IACs. It also provides a hypothetical scenario to which the law can be applied.