French army officer and engineer.

Entered the royal corps of engineers (1772). Joined Washington’s army at Valley Forge (spring 1778); served as chief subordinate of Baron von Steuben. Taken prisoner at fall of Charleston (May 1780); exchanged (January 1782). Returned to France as a full colonel (1784). Colonel of cavalry in the Dutch service (1785-88). Colonel of a French infantry regiment (1788-91). Served a brief term as French minister to the United States (1791-92) and remained in the United States for some time afterwards. Spoke perfect English. Plagued by ill health.

Son of Charles and Marie (de Lamarre) de Ternant of Damvillers (Meuse).