The Soviet Union was a massive country that existed from 1922 to 1991, covering roughly one-sixth of Earth's land surface. Its full name was the Union of Soviet Socialist Republics, or USSR for short. It stretched from Eastern Europe across northern Asia to the Pacific Ocean, making it the largest country in the world at the time.

The Soviet Union was created after a revolution overthrew Russia's emperor in 1917. The communist government that took power believed the state should control all property, businesses, and factories. Unlike democracies where citizens vote for their leaders and can criticize the government, the Soviet Union was ruled by a single political party that made all major decisions. People who disagreed with the government often faced severe punishment.

During much of the 1900s, the Soviet Union and the United States were superpowers locked in a rivalry called the Cold War. They never fought each other directly, but competed intensely in everything from space exploration to Olympic sports. The Soviets launched the first satellite (Sputnik) and sent the first human into space (Yuri Gagarin), pushing America to accelerate its own space program.

The Soviet Union eventually collapsed in 1991, splitting into fifteen separate countries, including Russia, Ukraine, and others. This happened partly because the communist economic system wasn't working well and partly because people in these regions wanted more freedom and independence.