World War II by country

Almost every country in the world participated in World War II. Most were neutral at the beginning, but only a relative few nations remained neutral to the end. The Second World War pitted two alliances against each other, the Axis powers and the Allied powers; the Soviet Union mobilised 34 million men and women, Germany 18 million, the U.S 16 million, Japan 9 million, and Great Britain 6 million. It is estimated that in total, 126 million people were mobilised during the war. It is generally estimated that a total of 72 million people died, with the lowest estimate being 40 million dead and the highest estimate being 90 million dead. The leading Axis powers were Nazi Germany, the Empire of Japan and the Kingdom of Italy; while the British Empire, the United States, the Soviet Union and China were the "Big Four" Allied powers.

The countries involved in or affected by World War II are listed here alphabetically, with a description of their role in the conflict.