Substate nationalism has noticeably affected the political and territorial stability of many countries, both democratic and democratizing, especially in the past fifteen years. The actors in conflicts of self-determination employ “nationhood” to identify themselves. Yet the fact that they claim national identity does not necessarily place them in the class of nations, nor does it immediately entitle them to self-determination. Judging the legitimacy of granting a particular group the right to self-determination requires determining first whether it in principle qualifies to advance the claim.Aclarification of how nationhood relates to self-determination and a commonly accepted definition of nationhood could introduce much-needed conceptual clarity to the assessment of substate groups’ entitlements and to the definition of the subjects of the right to self-determination. Presently, the very notion of “nation” is ambiguous. The word has several meanings, including “people,” “national minority,” “the population of a state,” “ethnic group,” and “title nation” or “majority.” The UN Charter declares the right of all peoples to self-determination, but “people” is not clearly defined and does not in principle exclude substate national groups from the entitlement. In current international practice and law, the terms “nation” and “state” are often used interchangeably. One document designed to protect national minorities, the European Framework Convention, for example, recognizes states as the undersigning parties and emphasizes its signatories’ respect for those states’ territorial integrity and national sovereignty. 1 Thus, the convention seems to introduce confusion between nationhood and statehood. International law overall does not define the status or the powers that non-state groups that claim to be nations in multinational states should have in relation to other groups, their citizens, and their own national minorities. The meaning of “national,” especially in light of terms like “national sovereignty,” needs to be clarified. My concern in this article is to offer a pragmatic definition of nationhood that can serve as an appropriate conceptual background for determining the status and norms for relations of national groups in multinational states. I do not defend any set of normative principles designed to regulate relations of self-determination among national groups. Rather, I first introduce two criteria that any definition of “nation” has to satisfy to be better at conceptualizing nationhood than the status quo, and I explain how rival conceptions of nationhood fail to satisfy the criteria. Then I put forward my definition of a nation—a collective agent characterized by a political culture of self-determination with which its members self-identify.