Joseph Ligon is an American convicted murderer and former prisoner. He was America's longest-serving prisoner who was convicted of two counts of first-degree murder by association and sentenced to life imprisonment without parole as a juvenile, at the age of 15. After the Supreme Court had ruled in Montgomery v. Louisiana that all mandatory juvenile life without parole sentences were retroactively unconstitutional, he was released without parole in February 2021 after a federal court vacated his sentence, having spent 68 years in prison.