The article examines the etymology of the word „unity”, the genesis of the idea of unity in Ukrainian political thought and scientific discourse, proposes the theoretical and methodological foundations of the research, and analyzes the evolution of the idea of unity in the discourses of political parties and presidents of Ukraine. It is about the evolution of the idea of unity throughout the entire process of Ukrainian state formation. Historical realities were of great importance for the formation and affirmation of the idea of unity, namely, the fragmentation of lands, foreign rule, the loss of the religious oneness of the people, and national oppressions. The evolution of the idea of the unity from the princely era to the present, from the idea of a united Rus to the idea of a free Independent United Ukraine, is traced, based on the research of domestic and foreign authors. Attention is focused on the symbolism of unity, markers of unity, traditions of holding „living chains” of unity as the main symbol of the Day of Unity, which Ukrainians build, symbolizing the unification of Ukrainian lands and state unity and the nationwide celebration of Unity Day. The Day of the Unity of Ukraine is characterized by the actualization of three dimensions of political meaning – past, present and future. The idea of unity was determined, first of all, by the unity of values, ideals and interests of the citizens of Ukraine. In the political discourse, emphasis was placed on the fact that the unity is a symbol of the unification of the country, as well as a reference point for the future as a territorial and spiritual unity of the people. In the addresses and speeches of the Presidents of Ukraine, the evolution from the idea of unity to the idea of oneness was traced. Presidents of Ukraine appealed to the lessons of the past and historical figures of Ukraine; they emphasized that the unity is an indivisible whole of all Ukrainian lands; noted that unity is not only about the territory, but also about oneness, cohesion, community. Preserving the territorial integrity of Ukraine, strengthening the unity of its regions, the diversity and distinction of which have developed as a result of objective historical circumstances, will continue to be a relevant, but also an urgent task of today.