Mỹ Lai Massacre: U.S. Army Lieutenant William Calley is charged with six specifications of premeditated murder for the death of 109 Vietnamese civilians in My Lai.

The My Lai massacre was a United States war crime committed on 16 March 1968, involving the mass murder of unarmed civilians in Sơn Mỹ village, Quảng Ngãi province, South Vietnam, during the Vietnam War. At least 347 and up to 504 civilians, almost all women, children, and elderly men, were murdered by U.S. Army soldiers from C Company, 1st Battalion, 20th Infantry Regiment, 11th Brigade and B Company, 4th Battalion, 3rd Infantry Regiment, 11th Brigade of the 23rd (Americal) Division. Some of the women were gang-raped and their bodies mutilated, and some soldiers mutilated and raped children as young as 12. The incident was the largest massacre of civilians by U.S. forces in the 20th century.

A lieutenant is a junior commissioned officer rank in the armed forces of many nations, as well as fire services, emergency medical services, security services and police forces.

William Laws Calley Jr. was a United States Army officer convicted by court-martial of the murder of 22 unarmed South Vietnamese civilians in the My Lai massacre on March 16, 1968, during the Vietnam War. Calley was released to house arrest under orders by President Richard Nixon three days after his conviction. The United States District Court for the Middle District of Georgia granted him a new trial, but that ruling was overturned by the United States Court of Appeals for the Fifth Circuit. His initial life sentence having been modified to a term of 20 years and then further reduced to ten, Calley ultimately served three years of house arrest for the murders. Public opinion at the time about Calley was divided. After his dismissal from the U.S. Army and release from confinement, Calley avoided public attention.

Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about 331,000 square kilometres (128,000 sq mi) and a population of over 100 million, making it the world's fifteenth-most populous country. One of two communist states in Southeast Asia, Vietnam shares land borders with China to the north, and Laos and Cambodia to the west. Its capital is Hanoi and its largest city is Ho Chi Minh City.