Étienne Nansouty was born in 1768 in a family of nobles. He studied at the Brienne school and graduated from the Paris Military College. He began his military career in the Bourgogne cavalry regiment as Sub-Lieutenant. Shortly after the Revolution of May 1792, he was promoted to Colonel of the 2nd Mounted Chasseurs regiment.
He was gifted with military talent and and had the persistence for prompt career progress. In 1800, he headed the Rhine army's right-wing cavalry. The troops under his leadership played an important role in the victory at Stockach. In 1805, Nausouty was appointed Commander of Boulogne, Louis Bonaparte's reserve heavy cavalry corps, and in 11 days, his division was re-formed into the 1st Cuirassier and Carabineer Division of the Grand Army's reserves.
Due to his leadership, this division was recognized as one of the best army units and proved itself in numerous battles. During the battle at Austerlitz, his cavaliers selflessly repelled furious assaults from the Russian and Austrian cavalry, and attacked the overwhelming enemy infantry forces. In the battle of Eckmuhl, Naunsouty carried out his well-known night attack, crushing the Austrian troops. Naunsouty's cavaliers gave an astonishing performance in the battles near Essling and Wagram. His cuirassiers fought with McDonald's troops, striking a major blow.
Naunsouty took part in campaign of 1812 as the commander of the 1st Reserve Cavalry Corps of the Grand Army and has been wounded during the Borodino battle. In 1813, he was appointed Commander of Emperor's Guard Cavalry and joined in several battles. He distinguished himself in the battle at Hanau, where he covered his army's retreat, allowing an organized withdrawal.
After the restoration of the Bourbons, he stayed in the army and received the title of King's Extraordinary Commissar in the 18th Military District, and the honorary rank of Lieutenant Commander of the 1st Company of Royal Musketeers and the rank of Dragoon Colonel General. Naunsouty died in 1815.