The Reapers' War, also known as the Catalan Revolt, was a conflict that affected the Principality of Catalonia between the years of 1640 and 1659. It had an enduring effect in the Treaty of the Pyrenees (1659), which ceded the County of Roussillon and the northern half of the County of Cerdanya to France, splitting these northern Catalan territories off from the Principality of Catalonia and the Crown of Aragon, and thereby receding the borders of Spain to the Pyrenees.

The Principality of Catalonia was a medieval and early modern state in the northeastern Iberian Peninsula. During most of its history it was in dynastic union with the Kingdom of Aragon, constituting together the Crown of Aragon. Between the 13th and the 18th centuries, it was bordered by the Kingdom of Aragon to the west, the Kingdom of Valencia to the south, the Kingdom of France and the feudal lordship of Andorra to the north and by the Mediterranean Sea to the east. The term Principality of Catalonia was official until the 1830s, when the Spanish government implemented the centralized provincial division, but remained in popular and informal contexts. Today, the term Principat (Principality) is used primarily to refer to the autonomous community of Catalonia in Spain, as distinct from the other Catalan Countries, and usually including the historical region of Roussillon in Southern France.