The term nation-state reflects both a geopolitical and a political entity. Nation refers to a sociocultural entity—peoples who share the same culture, history, and language; state refers to a legal and political entity that is a defined sovereign territory. While the origins and early history of the nation-state are disputed, most theories view the nation-state as a 19th-and 20th-century Western phenomenon deriving from the Treaty of Westphalia (1648), which many historians identify as marking the beginning of the modern European idea of a nation-state in which the national community and the sovereign ruler are identified as a single entity.

The earliest predecessors of modern nation-states are the city-states of ancient Greece, or polis. In the Medieval and Renaissance periods, this notion of localized government existed in ...