National identity is a person's identity or sense of belonging to one or more states or one or more nations. It is the sense of "a nation as a cohesive whole, as represented by distinctive traditions, culture, and language".

National identity comprises both political and cultural elements. As a collective phenomenon, it can arise from the presence of "common points" in people's daily lives: national symbols, language, the nation's history, national consciousness, and cultural artifacts. Subjectively, it is a feeling one shares with a group of people about a nation, regardless of one's legal citizenship status. In psychological terms, it is defined as an "awareness of difference", a "feeling and recognition of 'we' and 'they'". National identity can incorporate the population, as well as diaspora, of multi-ethnic states and societies that have a shared sense of common identity. Hyphenated ethnicities are examples of the confluence of multiple ethnic and national identities within a single person or entity.

Under international law, the term national identity, concerning states, is interchangeable with the term state's identity or sovereign identity of the state. A State's identity by definition, is related to the Constitutional name of the state used as a legal identification in international relations and an essential element of the state's international juridical personality. The sovereign identity of the nation also represents a common denominator for identification of the national culture or cultural identity, and under International Law, any external interference with the cultural identity or cultural beliefs and traditions appear to be inadmissible. Any deprivation or external modification of the cultural national identity violates basic collective human rights.

The expression of one's national identity seen in a positive light is patriotism characterized by national pride and the positive emotion of love for one's country. The extreme expression of national identity is chauvinism, which refers to the firm belief in the country's superiority and extreme loyalty toward one's country.

National identity is not an inborn trait; it is essentially a social construct. There is no agreed definition of what constitutes national identity. It can result from the presence of elements from the "common points" in people's daily lives: national symbols, languages, colors, national history, blood ties, culture, music, cuisine, radio, television, and so on. Under various social influences, people incorporate national identity into their identities by adopting beliefs, values, assumptions, and expectations which align with a national identity. People with identification with their nation view national beliefs and values as personally meaningful and translate them into daily practices.

Three main schools of defining national identity exist:

A few scholars have investigated how popular culture connects with the identity-building process. Some found that contemporary music genres can strengthen ethnic identity by increasing the feeling of ethnic pride.

Political scientist Rupert Emerson defined national identity as "a body of people who feel that they are a nation". This definition of national identity was endorsed by social psychologist, Henri Tajfel, who formulated social identity theory together with John Turner. Social identity theory adopts this definition of national identity and suggests that the conceptualization of national identity includes both self-categorization and affect. Self-categorization refers to identifying with a nation and viewing oneself as a member of a nation. The affect part refers to the emotion a person has with this identification, such as a sense of belonging or emotional attachment toward one's country. The mere awareness of belonging to a specific group invokes positive emotions about the group and leads to a tendency to act on behalf of that group, even when other group members are sometimes personally unknown.