The Franco-Spanish War (1635–1659) was a military conflict fought by France and Spain, with other powers participating at different points. The first phase which began in 1635 and ended with the 1648 Peace of Westphalia is considered a related conflict of the Thirty Years' War. The second phase continued until 1659 when France and Spain agreed the Treaty of the Pyrenees; most historians view its results as largely inconclusive.
Major areas of conflict included northern Italy, the Spanish Netherlands, and the German Rhineland. In addition, France supported revolts against Spanish rule in Portugal, Catalonia and Naples, while from 1647 to 1653 Spain backed French rebels in the civil war known as the Fronde. Both also backed opposing sides in the 1639 to 1642 Piedmontese Civil War.
France avoided direct participation in the Thirty Years' War until May 1635 when it declared war on Spain and the Holy Roman Empire, entering the conflict as an ally of the Dutch Republic and Sweden. After Westphalia in 1648, the war continued between Spain and France, with neither side able to achieve decisive victory.