In History and Political Science, "nation-state" is a term used to describe the principal historical agents on the world stage since the 17th century. For this purpose, a nation-state is defined as any state whose authority is based upon the dominance of a majority nationality, or on a set of shared national principles, which basically includes almost all modern nations as we have known them for the last several centuries. In this conception, the idea of the nation-state originated with the Peace of Westphalia in 1648, when states and international relations were defined for the first time in terms of nationality, rather than, for example, religious mandate or divine kingship. Out of this fledgling sense of nation grew the very concept of having a "nationality" as we know it and take for granted to this day, with all its associated trappings such as "citizenship," "patriotism," "passports," "borders," or "minorities."

In the standard historical periodization of western historiography, the concept of the nation-state is closely related to the Modern Period, and is considered one of the defining traits of "Modernity." This naturally begs the question that, if the world is supposedly entering the "Postmodern" period, whither the nation-state? Indeed, it is not surprising that many scholars have already heralded the demise or impending demise of the nation-state. Thinkers such as Jacques Derrida and others have postulated that the single defining attribute of the nation-state is the exercise of absolute coercive authority over its constituent members. For Derrida, this means the implementation of the death penalty and the ability to institute compulsory military service, and indeed these two powers have been characteristics of all nation-states up until very recently.

In an age of truly multinational corporations, an increasingly integrated European Union, influential NGO's such as Amnesty International and Greenpeace, and international terrorist organizations such as al-Qaida, the nation-state does seem to be receding from, or at least being forced to share, the world stage where historical actors perform and historical agency is assessed. Nevertheless, most people on Earth continue to use nationality as one of the primary, if not in fact the principal, means of defining themselves as human beings. If the nation-state is dying as a concept, it is certainly a drawn-out death scene, and it will be interesting to see how people clinging to models based on the nation-state will interact with the growing power of transnational agents - the prime current example being George W. Bush declaring a "War on Terror" and attempting to act as if he is at war with another state when in fact he is dealing with an amorphous non-Westphalian enemy that conceivably requires a wholly new set of rules and relations.