Florimond Claude, comte de Mercy-Argenteau (20 April 1727 – 25 August 1794) was an Austrian diplomat.
He was born in Liège, Belgium to Antoine, comte de Mercy-Argenteau, and entered the diplomatic service of Austria going to Paris in the train of ReichsfürstKaunitz. He became Austrian minister at Turin, at St Petersburg, and in 1766 at Paris, where his first work was to strengthen the alliance between France and Austria, which was cemented in 1770 by the marriage of the dauphin, afterwards Louis XVI, with Archduchess Maria Antonia of Austria, youngest daughter of Empress Maria Theresa. When four years later Louis and Marie Antoinette ascended the throne, Mercy-Argenteau became one of the most powerful personages at the French court by influencing and manipulating Marie-Antoinette, which made her unpopular with the French nobility and French people. He was in Paris during the turbulent years which heralded the French Revolution, and his powerful aid was given first to Loménie de Brienne, and then to Necker. In 1792 he became governor-general of the Austrian Netherlands, which had just been reduced to obedience by Austria, and here his ability and experience made him a very successful ruler. Although at first in favor of moderate courses, Mercy-Argenteau supported the action of Austria in making war upon his former ally after the outbreak of the French Revolution, and in July 1794 he was appointed Austrian ambassador to Britain, but he died a few days after his arrival in London.