A conscientious objector (often shortened to conchie) is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of thought, conscience, or religion.In some countries, conscientious objectors are assigned to an alternative civilian service as a substitute for conscription or military service.

On March 8, 1995, the United Nations Commission on Human Rights resolution 1995/83 stated that "persons performing military service should not be excluded from the right to have conscientious objections to military service". This was re-affirmed in 1998, when resolution 1998/77 recognized that "persons [already] performing military service may develop conscientious objections". A number of organizations around the world celebrate the principle on May 15 as International Conscientious Objection Day. The term has also been extended to objecting to working for the militaryindustrial complex due to a crisis of conscience.

Desmond Thomas Doss (February 7, 1919 – March 23, 2006) was a United States Army corporal who served as a combat medic with an infantry company in World War II. He was twice awarded the Bronze Star Medal for actions in Guam and the Philippines. Doss further distinguished himself in the Battle of Okinawa by saving 75 men, becoming the only conscientious objector to receive the Medal of Honor for his actions during the war. His life has been the subject of books, the documentary The Conscientious Objector, and the 2016 Oscar-winning film Hacksaw Ridge, where he was portrayed by Andrew Garfield.