Henri Philippe Benoni Omer Pétain (24 April 1856 – 23 July 1951), generally known as Philippe Pétain (, French: [filip petɛ̃]), Marshal Pétain (French: Maréchal Pétain) and sometimes The Old Marshal (French: le vieux Maréchal), was a French general officer who attained the position of Marshal of France at the end of World War I, during which he became known as The Lion of Verdun (French: le lion de Verdun). He then served as Chief of State of Vichy France from 1940 to 1944. Pétain, who was 84 years old in 1940, ranks as France's oldest head of state.

During World War I, Pétain led the French Army to victory at the nine-month-long Battle of Verdun. After the failed Nivelle Offensive and subsequent mutinies he was appointed Commander-in-Chief and succeeded in repairing the army's confidence. Pétain remained in command for the rest of the war and emerged as a national hero. During the interwar period he was head of the peacetime French Army, commanded joint Franco-Spanish operations during the Rif War and served twice as a government minister. During this time he was known as le vieux Maréchal (The Old Marshal).

With the imminent Fall of France and the Cabinet wanting to ask for an armistice, on 17 June 1940 Prime Minister Paul Reynaud resigned, recommending to President Albert Lebrun that he appoint Petain in his place, which he did that day, while the government was at Bordeaux. The Cabinet then resolved to sign armistice agreements with Germany and Italy. The entire government subsequently moved briefly to Clermont-Ferrand, then to the spa town of Vichy in central France. The government voted to transform the French Third Republic into the French State or Vichy France, an authoritarian regime that remained officially neutral in World War II but collaborated with the Axis. After Germany and Italy occupied and disarmed France in November 1942, Pétain's government worked very closely with Nazi Germany's military administration.

After the war, Pétain was tried and convicted for treason. He was originally sentenced to death, but due to his age and World War I service his sentence was commuted to life in prison. His journey from military obscurity, to hero of France during World War I, to collaborationist ruler during World War II, led his successor Charles de Gaulle to write that Pétain's life was "successively banal, then glorious, then deplorable, but never mediocre".