This thesis attempts to provide an overview of the origins of Northern Ireland in the context of its historical, geographical and geopolitical position. It also tries to establish how the migration of Protestants into the Irish island affected their coexistence with the local Catholic population and the extent to which the expansion of the immigrant population made the natives aware of their own religious affiliation. The paper also analyses political consequences of the population division into unionists, loyal to the Crown, and nationalists, willing to maintain a millennia-old relationship with Irish people. During the 20th century, the subordinate position of the Catholic inhabitants regarding employment, education and housing led to the political climate burdened by riots and armed conflicts verging on terrorist activity. Furthermore, the paper presents a review of Brexit – the United Kingdom’s exit from the European Union and what it means for Northern Ireland. It is important to note that Brexit does not express the will of the majority of the Northern Irish population. It can be assumed that in the context of separatist aspirations and the growing number of Catholics, the annexation to the Republic of Ireland is quite likely to happen. On the other hand, the value of Northern Ireland’s foreign trade activity is expected to lead to its impoverishment.