Abstract. European security today faces new challenges that are not directly related to military force. Among them, first of all, is the threat of terrorism, which has both internal and external dimensions. The article is devoted to the study of the phenomenon of terrorism in the European Union on the example of Italy. The author analyses four types of this threat posed by terrorists according to their political motivation: separatism, left- and right-wing domestic political terrorism, and Islamist terrorism. Italian law distinguishes between the concepts of terrorism, radicalism and subversion. According to the 2015 law, terrorism is defined as conduct that, by its nature or context, may cause serious harm to a country or an international organization. It is aimed at intimidating the population or forcing the State or international organizations to commit or refuse to commit any action. The evolution of the phenomenon of terrorism in Italy is of particular interest because it reflects both general and specific features of the terrorist threat in Europe. From the late 1960s to the 1970s and until the beginning of the 1980s, Italian society had been facing the most brutal manifestations of terrorism. During this period, terrorism evolved from ideological far-right extremism to ultra-left revolutionary extremism, which turns to violence against the State and its servants, calling for a communist transformation of society. By the end of the 1980s, the terrorist threat in Italy had been significantly reduced. The decline in terrorist activity in the 1980s is explained, in addition to the increased effectiveness of the intelligence services and the police, by the decline in political activity in Italy after the upheavals of the 1960s and 1970s. The author draws attention to one of the paradoxes of Islamist terrorism in Italy. Despite the fact that Italy bears the main flow of migration waves that can carry the threat of terrorism to Europe, the country has so far been spared from the large-scale threat of such kind. The example of Italy is also important because today the country’s leadership is the most effective in counterterrorism in comparison with other EU states.