The Chevalier d’Éon was born Charles d'Eon de Beaumont on October 5, 1728, and would go on to be a French soldier, spy, diplomat and in mid-life, a woman named Charlotte. D’Eon’s military exploits in the Seven Years’ War, role in negotiating the Paris Peace Treaty, and daring service as a spy for French King Louis XV was overshadowed by speculation about their gender.

Born biologically male, the Chevalier was legally declared female by French King Louis XVI and English courts and spent the last 33 years of their life as a woman. This famous figure blackmailed kings, fenced in dresses and courted controversy throughout their life—and after death.

D’Eon was born to a noble family in Tonnerre, Burgundy. After graduating from Collège Mazarin with a law degree in 1749, the 21-year-old gained a literary reputation with their political writings.

In 1756, d’Eon was recruited for the Secret du Roi, or King's Secret, a network of spies working for French King Louis XV. D’Eon was sent to Russia in two capacities: Officially, as Secretary of the Embassy in St. Petersburg. Secretly, the King tasked d’Eon with gathering intelligence in the court of Empress Elizabeth in a bid to put a Frenchman on the Polish throne.

The Empress was known for throwing weekly “metamorphosis balls” where men of the court dressed as women and noblewomen, as men. “In the medieval and early modern period, cross-dressing was much more socially accepted,” says Gary Kates, author of Monsieur d’Eon Is a Woman. “Every nobleman and noble lady would have known what it was like to cross-dress and did so all the time at masquerade balls.”

In later years, d’Eon would claim that, disguised as a woman, they served as a lady-in-waiting to Empress Elizabeth, but there is little historical evidence to confirm this. Regardless, d’Eon played a critical war in Franco-Russian relations, transporting top secret correspondence between King Louis XV in Versailles and Empress Elizabeth in St. Petersburg.

In September of 1756, Frederick the Great of Prussia invaded Saxony, kicking off the Seven Years’ War. D’Eon served France as Captain of Dragoons, earning a reputation as a brave soldier who was wounded in battle. In June 1763, d’Eon was named ambassador to Russia, plans that were dashed when Russian Emperor Peter III was assassinated and his wife, Catherine the Great, assumed power.

As the war dragged on, France’s debt mounted. In September of 1762, the King sent d’Eon to London as part of his diplomatic team to negotiate a peace. The Treaty of Paris was signed in Paris on February 10, 1763, and d’Eon was rewarded for his service to the crown with the Order of Saint-Louis. It came with a generous pension and the French title of chevalier, or “knight.”

After the British victory, King Louis XV was eager to restore France to her former glory. The newly minted Chevalier d’Eon was named Chargé d'Affaires and interim ambassador in London. D’Eon was also given an explosive secret mission: Identifying locations for a sea invasion of England even as the two Kings were publicly proclaiming peace. To get closer to the British nobility, d’Eon entertained lavishly, importing prized bottles of wine from his region of Burgundy and racking up enormous bills in the process.

D’Eon was enjoying a luxurious London lifestyle when their replacement, the Comte de Guerchy, was named and d’Eon was demoted to secretary. D’Eon was ordered to leave London and refused. Abandoning the post would jeopardize the secret invasion plans—plans D’Eon's replacement had no knowledge of. D’Eon insisted that only the King could recall them. “D’Eon had a huge ego,” says Kates. “They thought they were the best person for the job.”

When the King heard that d’Eon refused to step down, he froze d’Eon’s pension. An increasingly desperate Chevalier made a daring move: Blackmail.

In 1764, the Chevalier became the talk of London coffeehouses when they published the scandalous Lettres, mémoires et négociations particulières du chevalier d'Éon. It leaked private diplomatic correspondence that embarrased powerful figures, but stopped short of exposing the existence of the French spy network and the King’s plans to invade England. D’Eon knew the plans could spark war when he sent this extraordinary letter threatening to release them:

“[If] I do not receive a signed promise from the King or from the Comte de Broglie that the entire affair with M. De Guerchy has been resolved, well then, Monsieur, I will declare formally and truthfully that all hope is lost for me and that in forcing me into the arms of the King of England, his Prime Minister, and lords, it is obvious that you will be determining the fate of the next war, of which I will certainly be its innocent author, a war that will be inevitable…”

The letter was tantamount to treason, yet the King had to be careful; d’Eon was a popular figure in London with powerful friends. The delicate negotiations dragged on for over a decade. When Louis XV died on May 10, 1774, it remained to be seen how the new king would deal with d’Eon.

Meanwhile, rumors were swirling in London that the Chevalier was a woman. Popular broadsheets were printed portraying d’Eon as half man, half woman. The London Stock Exchange began taking bets on the Chevalier’s gender. Rather than refute the statements, the Chevalier fanned the flames, even challenging a prominent banker to a duel.

“D’Eon started to manipulate the press as [they] were falling from grace with [their] paymasters in France,” says Dr. Valerie Mainz, co-editor of The Chevalier d'Eon and his Worlds: Gender, Espionage and Politics in the Eighteenth Century. The publication of d’Eons book made them a celebrity in London; the speculation around their gender made d’Eon a household name. Mentions of the controversy have been found in diaries of young women and even letters from the King of France himself, who wrote to his general in 1770: “Do you know… that d’Eon is a girl?” The scandal was getting too big for the French government to ignore.

“Louis XVI was incentivized to make d’Eon happy,” says Kates. “He was a young king who had just come to the throne and had to clean up the mess left by his grandfather. He knew if the secrets d’Eon had were revealed to the public, there was a good chance England would go to war with France, and he needed breathing room to rebuild the economy.”

The King agreed to let d’Eon return to France and offered a life annuity of 12,000 livres a year if they surrendered the documents, left de Guerchy alone … and agreed to dress as a woman for the rest of their life in exchange for being legally proclaimed female.

“Louis 16th thought d’Eon really was and had always been a woman,” Kates says. Plus, declaring d’Eon legally female was politically expedient: “There weren’t women ambassadors or diplomats, so d’Eon couldn’t rise to power again. It was a clever way of marginalizing [them],” Mainz says. The Transaction, as the agreement came to be known, was signed in 1775.

At this point, d’Eon was still wearing male clothing. The King commanded his wife Marie-Antoinette’s personal dressmaker, Rose Bertin, to create a new wardrobe for d’Eon fit for a noblewoman. The transition wasn’t easy: “These ladies, to bring me to my predetermined point of perfection, make me suffer martyrdom so as to transform me into an elegant woman,” d’Eon complained. “It is more difficult to equip a lady than a company of Dragoons from head to foot.”

France had publicly proclaimed d’Eon a woman, and England soon followed in a widely publicized court case. “She is the most extraordinary person of the age,” wrote Edmund Burke in his London paper, The Annual Register. “We have several times seen women metamorphosed into men, and doing their duty in the war, but we have seen no one who has united so many military, political, and literary talents.” Sought out by Benjamin Franklin, Voltaire, and Rousseau, d’Eon was a cause célèbre in Europe.

“D’Eon not only crossed the gender barrier, living every day of their life as a woman from age 49-82, they did so as a public celebrity, not in domestic retirement,” says Kates. “D’Eon needed narratives that the European public would accept to explain their gender behavior.” D’Eon claimed they had been born female and were forced to conceal their gender by their father so they could inherit his estate. D’Eon maintained that they continued to dress as a man in order to gain glory for France as a diplomat and soldier. “D’Eon sets [themselves] up as a model for other strong women in the tradition of the femme forte,” says Mainz, a tradition that included Joan of Arc and the Amazons praised by Herodotus.

Mary Wollstonecraft singled out d’Eon in The Vindication of The Rights of Woman as a paragon of what was possible when women were given equal access to education. “For early feminists like Mary Wollstonecraft and her generation, d’Eon proved that if women were given the same opportunities as men in terms of education and training, there is nothing they can’t do,” says Kates.

During The French Revolution, d’Eon’s family estate in Tonnerre was seized and King Louis XVI executed. With the Transaction nullified, d’Eon was left with no pension and no home but was now legally free to dress as they pleased. D’Eon chose to dress exclusively as a woman for the final 33 years of their life. In London, d’Eon supported themselves by fencing in women’s clothing. When France entered the American Revolution on the side of the colonists in 1778, d’Eon offered to lead an army of women. The offer was declined.

D’Eon became increasingly religious and began writing their memoirs, which were not published in their lifetime. “What I am writing is not for the feeble souls of this century,” d’Eon wrote. “How much I have suffered in body and soul. All that I know is that my transformation has made me into a new creature.”

D’Eon died in poverty on May 21, 1810. Their body was discovered by their roommate of 14 years, a Mrs. Cole, who was so shocked by what she saw that she called in medical professionals who determined that d’Eon was biologically male. The press seized on the story: “They painted d’Eon as one of the greatest con men in history—an actor who made people believe something that was utterly untrue,” says Kates. “That narrative dominates the discourse on d’Eon in the 19th century until new ideas about sexuality retrieve d’Eon as not a faker, but someone who was exploring their gender identity,” says Kates. “D’Eon is still a popular figure in the media and pop culture and is regarded as a founding figure in the transgender community.”