The Brittany campaign, or the campaign of Brittany, was a military occupation of the Brittany, France, by Spain. It began in summer 1590 when Philippe-Emmanuel de Lorraine, Duke of Mercœur, the governor of Brittany, offered the port of Blavet to King Philip II of Spain so that he could harbour his fleet. The occupation formally ended on May 2, 1598, with the Peace of Vervins.
The Spanish used it as a base of operations to protect the treasure fleets, frustrate English naval operations, make incursions along the English coast and aid the Catholic League, all with the ultimate goal being the invasion of England.