The Palatinate campaign, also known as the Spanish conquest of the Palatinate or the Palatinate phase of the Thirty Years' War was a campaign conducted by the Imperial army of the Holy Roman Empire against the Protestant Union in the Lower Palatinate, during the Thirty Years' War.

The Thirty Years' War was one of the longest and most destructive conflicts in European history, lasting from 1618 to 1648. Fought primarily in Central Europe, an estimated 4.5 to 8 million soldiers and civilians died as a result of battle, famine, or disease, while parts of present-day Germany reported population declines of over 50%. Related conflicts include the Eighty Years' War, the War of the Mantuan Succession, the Franco-Spanish War, the Torstenson War, the Dutch-Portuguese War, and the Portuguese Restoration War.