A civilian grand jury on Thursday charged Steven Green, 21, and four other soldiers who are still in the army.
The case concerns Abeer Qasim Hamza al-Janabi, 14, who was sexually abused and then killed with her father, mother and six-year-old sister.
Green is further accused of trying to burn the bodies to conceal the crime.
Another soldier is charged with covering up the crime which took place on March 12, 2006, in Mahmudiya, Iraq.
Among the charges brought against Green were murder, murder in perpetration of aggravated sexual abuse, conspiracy charges, sexual abuse of a minor, and obstruction of justice.
If convicted, Green, who was discharged from the army's 101st Airborne Division for a "personality disorder", could receive the death penalty, prosecutors said in a statement.
He is to appear before the US district court in Louisville, Kentucky, on Wednesday.
The others charged in the gang-rape and murder face court-martial at Fort Campbell, Kentucky, home of the 101st Airborne Division, with some facing the death penalty.
The Mahmudiya case is one of several in which US servicemen are suspected of killing Iraqi civilians. It sparked outrage among Iraqis and prompted Iraqi officials to call for a review of foreign troops' immunity from Iraqi prosecution.