- Political prisoners: dissidents, activists, and individuals deemed a threat to the regime
- Ethnic and religious minorities: groups targeted due to their ethnicity or religious beliefs
- Forced laborers: individuals compelled to perform grueling and often dangerous work
- Prisoners of war: captured enemy combatants or civilians from occupied territories
- Other persecuted groups: certain LGBTQ+ individuals, disabled people, and others deemed undesirable by the regime in power.
Examples of well-known concentration camps include those established during the Holocaust, where millions of Jews, Romani people, and other minority groups were systematically exterminated. Other notorious examples include camps during the Soviet era, where political prisoners and dissidents were held, and more recent cases like the detention of Uighur Muslims in China.