[3] D'Éon's mother, Françoise de Charanton, was the daughter of a Commissioner General to the armies of the wars of Spain and Italy.

According to d'Éon's memoirs (although there is no documentary evidence to support that account) the monarch sent d'Éon with the Chevalier Douglas, Alexander Peter Mackenzie Douglas, Baron of Kildin, a Scottish Jacobite in French service, on a secret mission to Russia in order to meet Empress Elizabeth and conspire with the pro-French faction against the Habsburg monarchy.

D'Éon later claimed having to pass convincingly as a woman or risk being executed by the English upon discovery and therefore travelled disguised as the lady Lia de Beaumont, and served as a maid of honour to the Empress.

However, there is little or no evidence to support this and it is now commonly accepted to be a story told to demonstrate how identifying as female had been of benefit to France in the past.

After Empress Elizabeth died in January 1762, d'Éon was considered for further service in Russia, but instead was appointed secretary to the duc de Nivernais, awarded 1,000 livres, and sent to London to draft the peace treaty that formally ended the Seven Years' War.

Back in London, d'Éon became chargé d'affaires in April 1763, and then plenipotentiary minister—essentially interim ambassador—when the duc de Nivernais returned to Paris in July.

[8] Upon the arrival of the new ambassador, the comte de Guerchy in October 1763, d'Éon was demoted to the rank of secretary and humiliated by the count.

The British government declined a French request to extradite d'Éon, and the 2,000 livres pension that had been granted in 1760 was stopped in February 1764.

Following the death of Louis XV in 1774, the Secret du Roi was abolished, and d'Éon tried to negotiate a return from exile.

The desire to see his native land once more determined him to submit to the condition, but he revenged himself by combining the long train of his gown and the three deep ruffles on his sleeves with the attitude and conversation of a grenadier, which made him very disagreeable company."

The pension that Louis XV had granted was ended by the French Revolution, and d'Éon had to sell personal possessions, including books, jewellery and plate.

[10] In 1804, d'Éon was sent to a debtors' prison for five months, and signed a contract for a biography to be written by Thomas William Plummer, which was never published.

D'Éon became paralysed following a fall, and spent a final four years bedridden, dying in poverty in London on 21 May 1810 at the age of 81.

[10] The surgeon who examined d'Éon's body attested in their post-mortem certificate that the Chevalier had "male organs in every respect perfectly formed", while at the same time displaying feminine characteristics.

[15] Havelock Ellis coined the term eonism to describe similar cases of transgender behaviour; it is rarely used now.

[18] The Burdett-Coutts Memorial at St Pancras Gardens in London commemorates d'Éon as well as other people; in 2016 Historic England upgraded it to a Grade II* listed structure.