French army officer.
Sous-lieutenant of cavalry (1769); rose to the rank of maréchal de camp (1791). Traveled to United States (1782-83), where he served as mestre de camp in a regiment of dragoons. Ambassador to Russia (1784-89). Rose to political prominence under Napoleon as grand master of ceremonies (1805) and senator (1813).
Son of Philippe-Henri and Louise-Anne- Madeleine (de Vernon), marquis and marquise de Ségur. Married Antoinette-Elisabeth-Marie d’Aguesseau (1777); four children.