Brégy was born the eldest son of a president of the chambre des comptes. In 1637 he became councilor in the Parlement of Paris and in 1644 conseiller du roi. In 1645 he was sent on missions to Poland and Sweden, where Queen Christina appointed him capitaine des gardes. In March 1649, he was to join a French embassy to Constantinople, but he returned to France (December 1649), took service in the army, and eventually became lieutenant general (1655). Nothing is known about his later years except that he died November 22, 1689. His wife Charlotte de Chazans (1619–93) was known as a poetess. During the short period that Descartes and Brégy were together in Sweden they became friends (AT V 454–55). Descartes wrote Brégy after the latter left Sweden (AT V 455–57). To prevent his letter from being lost in the mail, he included a ballet to be performed the next evening. This has led some to believe that Descartes wrote a ballet. However, the ballet actually performed in Stockholm on December 9, 1649, was a German translation (by Freinsheim) of a French original by Hélie Poirier: Die Uberwundene Liebe (Love defeated). On January 15, 1650, Descartes wrote again, complaining that during the Swedish winter “human thoughts freeze as easily as water,” and announcing that he will not wait for Brégy's return (expected in March) to go back (AT V 467, CSMK 383).

See also Christina, Queen of Sweden