William Calley (born June 8, 1943) was an American Army lieutenant in the Vietnam War who was involved with the March 1968 My Lai Massacre.

Calley was charged on September 5, 1969 with six specifications of premeditated murder for the death of 109 Vietnamese civilians in My Lai. His trial started on November 17, 1969 and resulted in a conviction on March 29, 1971 of premeditated murder for his role in the massacre. Calley ordered the men of Charlie Company, 1st Battalion, American Division to shoot everyone in the village.

Calley was seen by some as a scapegoat for the Army's failure to instill morale and discipline in its troops. Nevertheless, despite having ordered his troops to commit a massacre, he ultimately received a light sentence. He was initially sentenced to life in prison, but President Richard Nixon ordered him released from prison. Calley served 3 1/2 years of house arrest in his quarters at Fort Benning, Georgia and was then released in 1974 by a federal judge.

See also: Vietnam War