International Criminal Law seeks to avoid impunity regarding the most grave and atrocious conducts that “threaten the peace, the security, and the well-being of the world”. These conducts, known as the core crimes of international law, refer to war crimes, crimes against humanity, genocide and aggression. Neither the Charter of Nuremberg, nor the Charter of Tokyo, the Statute of the International Tribunal for the former Yugoslavia, or the Rome Statute of the International Criminal Court, establish terrorism as a crime of their jurisdiction; it is not either established as a crime of international law in the Nuremberg Principles. Only the Statute of the International Tribunal for Rwanda establishes in its article 4 the “act of terrorism” as a crime of its competence. Through a process of research and analysis of treaties, customs and international law, it is alleged that acts of terrorism occurred during the first half of the 20th century; the treatment that international criminal law gave (Nuremberg, Tokyo) and gives (International Criminal Court, International Criminal Tribunal for the former Yugoslavia and International Criminal Tribunal for Rwanda) to those cases is described as well. Allegedly, terrorism is not alien to International Criminal Law, neither from a factual perspective nor from a legal one. Whether its regulation as an autonomous crime of international law is necessary or not is a discussion that goes beyond the purpose of this paper directed exclusively to evidence the relation between terrorism and International Criminal Law from a factual perspective and a legal one as well. This is done with the starting point of the identification of facts that constituted terrorism, in a specific historical context, and the legal response given by the international society, through the International Criminal Tribunals. Derecho Penal Internacional y Terrorismo: ?crimen de Derecho Internacional? Revista FACULTAD DE DERECHO Y CIENCIAS POLITICAS. Vol. 40, No. 113 (2010) / 383