b. 20 April 1752, Villard (Savoy)
d. 11 November 1824, Beauregard
Marquis de Saint-Genis. "Born in the chateau of Villard (Savoy) ... he entered military service on 17 June 1771 as an officer attached to the legion of encampments, a corps analogous to that of the engineer-topographers in France. He retired a few years later, in 1777, after his marriage to Mlle de Murinais, to the chateau of Beauregard on the shores of Lac Leman, and took its name. Having returned to the service in the spring of 1792 as a captain in the legion of encampments, in which his oldest son, Eugène, was already a second lieutenant at the age of fourteen years, the Marquis Costa participated in all the campaigns in the Alps and was promoted, while his family emigrated to Lausanne after the French conquest of Savoy. Appointed chief of staff to Colli's corps on 15 May 1794, then of the army in February 1795, he assisted Colli, having with him his second son, Victor, who had come to replace the elder, who had died in Turin in May 1794 as a consequence of the wounds he had received at the combat of La Saccarella. He accompanied General La Tour to Cherasco to negotiate the armistice, and then rejoined the staff of the Duke of Aosta, who had become commander in chief, then returned to Beauregard. In 1797, he became chief of staff of the army again, was then a member of the council of regents, in Turin, in 1799, and definitively retired from the service after Marengo." Bouvier, F. Bonaparte en Italie, 1796, Paris, 1899, pp. 676-7.
It is stated elsewhere that Costa had literary and artistic interests, and approved of Rousseau.