The military history of Switzerland comprises centuries of armed actions, and the role of the Swiss military in conflicts and peacekeeping worldwide. Despite maintaining neutrality since its independence from the Holy Roman Empire in 1499, Switzerland has been involved in military operations dating back to the hiring of Swiss mercenaries by foreign nations, including the Papal States.

The Swiss mercenaries were a powerful infantry force constituted by professional soldiers originating from the cantons of the Old Swiss Confederacy. They were notable for their service in foreign armies, especially among the military forces of the kings of France, throughout the early modern period of European history, from the Late Middle Ages into the Renaissance. Their service as mercenaries was at its peak during the Renaissance, when their proven battlefield capabilities made them sought-after mercenary troops. There followed a period of decline, as technological and organizational advances counteracted the Swiss' advantages. Switzerland's military isolationism largely put an end to organized mercenary activity; the principal remnant of the practice is the Pontifical Swiss Guard at the Vatican.