Nationalism is an ideology or 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-determination) over its perceived homeland to create a nation-state. It holds that the nation should govern itself, free from outside interference (self-governance), 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, homeland, language, politics (or government), religion, traditions or belief in a shared singular history, and to promote national unity or solidarity. There are various definitions of a "nation", which leads to different types of nationalism. The two main divergent forms are ethnic nationalism and civic nationalism.
The moral value of nationalism, the relationship between nationalism and patriotism, and the compatibility of nationalism and cosmopolitanism are all subjects of philosophical debate. Nationalism can be combined with diverse political goals and ideologies such as conservatism (national conservatism and right-wing populism) or socialism (left-wing nationalism).