Nationalism is the belief that nationality is the proper focus of political identity and that the nation-state is the proper focus of political loyalty. This sentiment expresses itself variously in separatist movements, which advocate political self-determination for people of a certain cultural heritage (primarily language); in irredentist claims on territories historically or ethnically belonging to the nation; and in movements to save the national identity from being diluted or altered by immigration.

Nationalism can fall on the right, left or center of the political spectrum. Generally, left-wing nationalists are of the "national liberation" variety. Right-wing nationalists aim to prevent the loss of national sovereignty to supranational entities such as the European Union, and to prevent the loss of national identity through mass immigration. However, there are exceptions, and there can be right-wing national-liberation movements, or left-wing nationalist movements in existing nation states.