Havelock Ellis coined the term eonism to describe similar cases of transgender behavior though it is rarely used now. The Beaumont Society, a long-standing organization for transgender people, is named after d'Éon.
D'Eon moved to Paris in 1743 and attended the Collège Mazarin in 1749 studying civil and canon law. D'Eon served as the secretary to the intendant of Paris, the administrator of the fiscal department, and appointed a royal censor for history and literature in 1758. In 1756, d'Eon joined the Secret du Roi (King's Secret), a network of spies employed by King Louis XV without knowledge of the government. According to d'Eon's memoirs, LouisXV sent a team of the Secret du Roi to Russia. In that time, England and France were opposing forces and the English made great efforts to prohibit access to Empress Elizabeth, the leader of Russia. The English were only allowing women and children to cross the border into Russia, so D'Eon had to pass convincingly as a woman or risk execution upon being discovered. D'Eon crossed the border into Russia as Lea de Beaumont and served as a maid of honor to the Empress.
D'Eon returned to France in 1760 and was highly rewarded for serving in Russia. In 1761, d'Eon was appointed as a captain of dragoons and fought in the later part of the Seven Years War. D'Eon was also sent to draft a treaty that brought that war to a close. In 1763, d'Eon was honored with Order of Saint-Louis and was given the title Chevalier d'Eon...a title similar to knighthood. The Chevalier spent many years exiled in London, the consequence of being trapped between opposing French factions regarding the suspicion and discovery of the Secret du Roi. King Louis XV died in 1774, and afterward, d'Eon attempted to negotiate a return to France. Agreements were made that required d'Eon to turn over all correspondence of the Secret du Roi. When the Chevalier d'Éon claimed to have been assigned female at birth and demanded the government recognize d'Eon as female. King Louis XVI and his court obliged, but required that d'Éon dress appropriately in women's clothing, although d'Éon was allowed to continue to wear the insignia of the Order of Saint-Louis. When the king's offer included funds for a new wardrobe of women's clothes, d'Eon agreed. After fourteen months of negotiation, d'Éon returned to France and as punishment was banished to Tonnerre in 1777.
When the French Revolution arose, d'Eon fell slowly into poverty as the government that had established d'Eon's pension was now defunct. D'Eon competed in fencing tournaments to survive until suffering a serious injury in 1796. In 1804, d'Eon became paralyzed and remained bedridden for the rest of their life. D'Eon died in poverty at the age of 81 in 1810.D'Éon's body was buried in the graveyard of St Pancras Old Church, and d'Éon's remaining possessions were sold by Christie's in 1813. D'Éon's grave is listed as one of the important graves lost at the Burdett-Coutts Memorial.
The Chevalier has been portrayed in a variety of media, including dramatic and comedic plays, a comic opera, film, an audio play and even manga and anime. D'Eon's life is a view into how transgender people are treated today and also can give us hope that we can accomplish great things and possibly even be honored for our efforts despite the situations we live through.