Gordian III AE Sestertius. Gordian III was a Roman emperor who reigned from 238 to 244 AD during the tumultuous period known as the Crisis of the Third Century. He was the youngest emperor in Roman history, ascending to the throne at the age of 13 after the death of his grandfather, Gordian I, and his father, Gordian II, in a short-lived rebellion against the emperor Maximinus Thrax.