The Appeal of 18 June (L'Appel du 18 Juin) was a famous speech by Charles de Gaulle, the leader of the Free French Forces, in 1940. The appeal is often considered to be the origin of the French Resistance to the German occupation during World War II. De Gaulle spoke to the French people from London after the fall of France. He declared that the war for France was not yet over, and rallied the country in support of the Resistance. It is one of the most important speeches in French history.

In spite of its reputation as the beginning of the Resistance and Free French, historians have shown that the appeal was heard only by a minority of French people. De Gaulle's 22 June 1940 speech on the BBC was much more widely heard.

General de Gaulle became the de facto leader of the Free French Forces which had escaped to London in June 1940. Marshal Philippe Pétain, a hero of World War I, had signed an armistice with Nazi Germany, and led the collaborating Vichy government while the Germans occupied the country's northern portion. De Gaulle opposed the armistice and had fled France on 15 June after Pétain made clear that he would seek an accommodation with the Nazis.