The Swedish invasion of the Holy Roman Empire, or the Swedish Intervention in the Thirty Years' War, that takes place between 1630 and 1635 is a major turning point of the war, often considered to be an independent conflict.

After several attempts by the Holy Roman Empire to prevent the spread of Protestantism in Europe, King Gustav II Adolf of Sweden orders a full-scale invasion of the Catholic states.

Although he is killed in action, his armies successfully defeat their enemies and give birth to the Swedish Empire after proving their ability in combat.

The new European great power will last for a hundred years before being overwhelmed by numerous enemies in the Great Northern War.