The Right to Self-Determination is a fundamental Human Right which is respectfully recognized by all the three generations of the human rights and the international community. This issue indicates the importance of the right in the context of human rights dialogue. Considering such a place for a human right shows its high level of legitimacy in the international law. Whereas knowing about the philosophical background of the right to self-determination promote its normative strength and gives it a great higher credit in the international world, this article is trying to define the philosophical bases of the right to self-determination and explain the basis of its legitimacy. To answer the question about the basis of the legitimacy of this right, it will be concluded that the analysis of the right in the framework of philosophy of the international law, by theorizing it in the context of the concepts like collective rights, rationalism, justice, globalization and third-worldism which the right to self-determination has been stabled according to them, will demonstrate its legitimacy as it deserves it.