The neutral powers were countries that remained neutral during World War II. Some of these countries had large colonies abroad or had great economic power. Spain had just been through its civil war, which ended on 1 April 1939 —a war that involved several countries that subsequently participated in World War II.

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. It is estimated that 74 million people died, with estimates ranging from 40 million to 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.