National service is a form of military service that is typically compulsory for citizens of a country. It involves the conscription of citizens into the military or other national service programs, such as public works, education, or health care. In some countries, national service is voluntary and may involve alternative forms of service such as civilian service or community service.

In many countries, national service has been used to promote patriotism and national identity, to provide training and skills for young people, and to help build infrastructure. It has also been used to fill gaps in the labor force during wartime and other times of need. In some cases, it has been used as a punishment for criminal activity.

The duration of national service varies from country to country; in some cases it may last only a few months while in others it may last several years. Some countries have abolished their national service programs entirely while others have kept them in place but modified them over time.