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 in Paris in the train of ReichsfürstKaunitz. He became Austrian minister in Turin at the court of King Charles Emmanuel III of Sardinia, in St. Petersburg at the court of Catherine the Great, and then Paris at the court of King Louis XV of France in 1766. In Paris, 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, afterwards known as Queen Marie Antoinette. When Louis and Marie Antoinette ascended the throne of France in 1774, Mercy-Argenteau became one of the most powerful personages at the French court due to his influence over Marie-Antoinette, which made her unpopular with the French nobility and French people. He was in Paris during the turbulent years the heralded the French Revolution, and gave powerful aid to the finance ministers Loménie de Brienne and Necker. In 1792, he became governor-general of the Austrian Netherlands, which had just been reduced to obedience by Austria. There, 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.