Armand Emmanuel Sophie Septimanie de Vignerot du Plessis, 5th Duke of Richelieu and Fronsac (25 September 1766 – 17 May 1822), was a French statesman during the Bourbon Restoration.

His father was the son and heir of King Louis XV of France's favourite, Armand de Vignerot du Plessis, 3rd Duke of Richelieu.

[4] On Marie Antoinette's direction, he left Paris in 1790 for Vienna to discuss the recent events of the French Revolution with her older brother, the Holy Roman Emperor Joseph II.

Because of an unwillingness on the part of various nobles to serve in the royal household, King Louis XVI soon afterwards summoned him back to Paris in order for him to resume his position as a premier gentilhomme at the Tuileries Palace.

[2] Feeling that his role at court was useless in helping the King deal with all the revolutionary agitation that was embroiling Paris, Richelieu in July obtained with royal permission a passport from the National Constituent Assembly in order to return to Vienna as a diplomat.

After a short stay in Austria, however, Richelieu joined the counter-revolutionary émigré army of Louis XVI's cousin, the Prince of Condé, which was headquartered in the German frontier town of Koblenz.

Two years later, he became Governor-General of a large swathe of land recently conquered from the Ottoman Empire and called New Russia, which included the territories of Kherson, Ekaterinoslav and the Crimea.

[5][6] Dismissive of any attempt to forge a compromise between quarantine requirements and free trade, Prince Kuriakin (the Saint Petersburg-based High Commissioner for Sanitation) countermanded Richelieu's orders.

From there, he chose to return to Vienna in order to rejoin the Russian army, believing that he could best serve the interests of the new king and of France by attaching himself to the headquarters of Tsar Alexander.

Though the bulk of his confiscated estates were lost beyond recall, he did not share the angry resentment of most of the returning émigrés, from whose company and intrigues he had held himself aloof during his long Russian exile.

In order to achieve this goal, he attended the Congress of Aix-la-Chapelle in 1818, where he was informed in confidence of an Allied pledge to interfere internally in France if a revival of revolutionary trouble was to occur.

After the murder of the king's nephew, the Duke of Berry, and the enforced retirement of Decazes, he was again called to the premiership (21 February 1821); but his position was untenable due to political attacks from the "Ultras" on one side and the Liberals on the other.