hastellux was born in Paris, France. At age 13, he joined the army as a second lieutenant and rose through the ranks during the Seven Years' War. With military glory, he also gained literary fame. Chastellux was given membership in the French Academy after publishing a book of philosophy in 1772. When the French expeditionary forces assigned to the Revolutionary Continental Army set sail for America in 1779, he was one of the three major generals sent with General Rochambeau. They arrived in America and took part in the victorious Yorktown campaign. Chastellux's fluency in English made him invaluable to the Continental Army commanders.

fter the Revolution, Chastellux returned to France and published his reminiscences, Travels in North America. He became military governor of Longwy, as well as an Inspector General in the army. In 1784, he succeeded his brother as the Marquis de Chastellux. He died in Paris on October 24, 1788.