Greek nationalism, otherwise referred to as Hellenic nationalism, refers to the nationalism of Greeks and Greek culture. As an ideology, Greek nationalism originated and evolved in classical Greece. In modern times, Greek nationalism became a major political movement beginning in the early 19th century, which culminated in the Greek War of Independence (1821–1829) against the Ottoman Empire.

Nationalism is an idea and movement that holds that the Nation should be congruent with the state. As a movement, it presupposes the existence and tends to promote the interests of a particular nation, especially with the aim of gaining and maintaining its sovereignty (self-governance) over its perceived homeland to create a nation-state. It holds that each nation should govern itself, free from outside interference (self-determination), that a nation is a natural and ideal basis for a polity, and that the nation is the only rightful source of political power. It further aims to build and maintain a single national identity, based on a combination of shared social characteristics such as culture, ethnicity, geographic location, language, politics, religion, traditions and belief in a shared singular history, and to promote national unity or solidarity. Nationalism, therefore, seeks to preserve and foster a nation's traditional culture. There are various definitions of a "nation", which leads to different types of nationalism. The two main divergent forms identified by scholars are ethnic nationalism and civic nationalism.