Who was on the side of the allies in World War 2?

Answer 1

Britain, USSR, Stalin, United States, Russia and a few small countries like Italy too.
There were many nations fighting against the Axis Powers including; the British Empire, France (eventually the Free French under Charles De Gaulle), Poland, the Soviet Union, both Nationalist and Communist China, Australia, New Zealand, South Africa, Belgium, Netherlands, Luxembourg, Brazil, Canada, Nepal, Bolivia, Colombia, Mexico and the United States are the major contributors to the Allied war effort.

Obvious answer: Allies.
The vast majority of the countries of the world were at least at some point members of the allied side, but the most important allied countries from a military point of view were USA, United Kingdom, France, the Soviet Union, Canada, Australia and China.