United States. Franklin Delano Roosevelt, President. General Dwight D. Eisenhower, Supreme Commander.
Great Britain. King George VI. Winston Churchill, Prime Minister. General Bernard Montgomery, commander of British forces. Also included: Canada, Australia, New Zealand, India, Union of South Africa, Cyprus and others.
Soviet Union. Joseph Stalin.
China. Generalissimo Chiang Kai-shek
France. President Albert Lebrun (until 1940). General Charles De Gaulle, Free French Forces.
Poland. President Ignacy Mościcki.
Brazil. President Getúlio Vargas
Yugoslavia. Josip Tito.
Other Allied participants included Norway, the Netherlands, Mexico, Greece, Ethiopia, Czechoslavakia, and Belgium.
Germany. Chancellor Adolph Hitler.
Italy. Dictator Benito Mussiolini.
Japan. Emperor Hirohito
Other participants included Hungary, Romania, Bulgaria, Finland, Iraq, Thailand, San Marino, Yugoslavia; there were also many Japanese, German and Italian "puppet" states involved.
While there were many countries involved in World War II on both sides, only a few of them were really relevant to the course of the war as a whole. I will list the major countries for each side and their leaders.
On the Axis side, there were three major countries at the beginning of the war. These were Japan, Germany, and Italy. Germany and Italy were fascist dictatorships. Their leaders were Adolf Hitler and Benito Mussolini, respectively. Japan's leader is harder to identify. The head of state was the Emperor Hirohito. However, he was more of a figurehead than the other leaders mentioned here. Hideki Tojo was the Prime Minister and head of government for most of WWII. If Japan could be said to have had a single leader, it would have been Tojo.
On the Allied side, there were also three main countries as of December 8, 1941. By that point, France was no longer a major force on the Allied side. The main Allied powers were the Soviet Union, led by Josef Stalin, the United Kingdom, led by Winston Churchill, and the United States, led by Franklin D. Roosevelt.
The Axis powers are Germany, Italy, and Japan.The Hirohito,Duce Benito Mussolini and Adolf Hitler.France, Poland and the United Kingdom, soon to be joined by the British dominions (Australia, Canada, New Zealand, and South Africa). After 1941, the leaders of the United States of America, the British Commonwealth, and the Soviet Union known as the "Big Three".Three of the central Allied leaders, Winston Churchill, Franklin D. Roosevelt, and Joseph Stalin.