The paper is devoted to the analysis of the approaches of various states and international consultative and advisory bodies to holding referendums on the self-determination of the people. It has been revealed that the right to self-determination can be based not only on ethnicity, but also on other characteristics, including common historical heritage, ethnic unity and language of communication. With regard to self-determination in the form of secession, the importance of establishing the boundaries of secession is noted, historical examples of referendums in various parts of the world and their consequences are examined. There are five historically established features that can be considered as a reflection of the legitimacy of the ongoing referendum on self-determination: connection with historical background, defining the boundaries of the referendum, ensuring fundamental democratic rights, establishing a legal framework and limiting external interference or pressure on referendum participants. These elements together create the conditions for obtaining legitimate results of the referendum and its subsequent meaning from the point of view of law.