Swiss military leader, spokesman for Roman Catholic interests in the cantons, and probably the most important Swiss political figure in the latter half of the 16th century.

For many years an active and intrepid warrior in the service of France, Pfyffer won fame by safely leading the royal family of Charles IX from Meaux to Paris while under Huguenot attack (1567). Elected chief magistrate for Luzern in 1571—which office he continued to occupy until his death—he made that city the centre of Catholic Counter-Reformation activity in Switzerland. His Golden (or Borromean) League (1586)—the alliance of the seven Catholic cantons for furtherance of religious interests—nearly led to the destruction of the Swiss Confederation and precipitated the division of the canton of Appenzell along religious lines. Pfyffer established close relations with the Holy League of Philip II of Spain and Henri, duc de Guise, and concluded a Swiss alliance with Spain (1587) against the accession of Henry of Navarre (Henry IV) to the French throne. He also acquired a substantial fortune from foreign pensions and as a supplier of mercenaries to the pope.