This research paper is an attempt to investigate the phenomenon of global terrorism and its threats to the security of the state. The study clarifies the concept of terrorism and it its definition, then the categories of terrorism. Next, it shows how terrorism became a global phenomenon through the historical overview of international terrorism and the theories explaining it and its current situation. The causes of international terrorism are the economic cause, social cause, religions cause, political cause and other causes. The study investigated the effects of international terrorism and its implications on international peace, states security and what had been done yet internationally in fighting terrorism. The study analyses the causes and the theoretical frameworks that stand behind the phenomenon. The study recommended to face the international terrorism through developing national strategies and strengthening international, regional and bilateral cooperation and coordination with the international counter-terrorism system in the context of the resolutions of the UN and building national intellectual system to confront terrorism and solving the major political conflicts which have direct impact on the terrorism.