A conscientious objector is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of conscience or religion. The term has also been extended to objecting to working for the military–industrial complex due to a crisis of conscience. In some countries, conscientious objectors are assigned to an alternative civilian service as a substitute for conscription or military service.

Conscription evasion or draft evasion is any successful attempt to elude a government-imposed obligation to serve in the military forces of one's nation. Sometimes draft evasion involves refusing to comply with the military draft laws of one's nation. Illegal draft evasion is said to have characterized every military conflict of the 20th and 21st centuries, in which at least one party of such conflict has enforced conscription. Such evasion is generally considered to be a criminal offense, and laws against it go back thousands of years.