Swiss mercenaries were Swiss soldiers-for-hire who served in the armies of Europe from the Renaissance era into the 19th century.
Swiss soldiers had obtained a reputation as skilled fighters after defeating the Austrians at the 1315 Battle of Morgarten and the 1339 Battle of Laupen, and the various Swiss cantons contracted their local militias out to foreign rulers amid the Burgundian Wars and the Italian Wars and for Matthias Corvinus' "Black Army". Swiss mercenaries primarily fought as pikemen during the Middle Ages, and they were renowned for taking no prisoners and for fighting to the death. The Swiss distinguished themselves at the Battle of Novara in 1513 and the 1515 Battle of Marignano, but the 1522 Battle of Bicocca shattered their prestige as the Spanish used firearms against them. After the 1525 Battle of Pavia, the German landsknechts eclipsed the Swiss pikemen in popularity.
Nevertheless, the French Royal Army maintained twelve Swiss mercenary regiments, including the Swiss Guards. During the War of the Austrian Succession, 20,000 Swiss soldiers fought for France, although the number fell to 12,300 after the end of the Seven Years' War. During the French Revolution, many French-speaking Swiss soldiers sympathized with the revolution. The Swiss Guards famously fought to the death while defending the Tuileries Palace from the 10 August insurrection of 1792. After the 1798 French invasion of Switzerland, six demi-brigades of Swiss infantry were raised for the French Revolutionary Army. During Napoleon's 1812-1813 retreat from Russia, the Swiss contingent suffered 80% losses. During the July Revolution of 1830, 300 Swiss soldiers were killed while defending the Fontainebleau and Louvre palaces, and all other Swiss units in French service were disbanded.
Habsburg Spain primarily recruited Catholic Swiss mercenaries, and a dozen regiments fought in the Dutch Revolt, the Portuguese Restoration War, the Reapers' War, and the War of the Grand Alliance. Swiss soldiers would serve in Italy during the War of the Quadruple Alliance and the War of the Polish Succession, while 30,000 Swiss troops fought there in the War of the Austrian Succession. By the 1790s, 13,000 Swiss troops were serving in the Spanish Army, but the French Revolutionary Wars disrupted recruitment from Switzerland and forced Spain to enlist Germans, Austrians, and Italians instead. The Swiss regiments suffered heavy losses during the Peninsular War, and they were disbanded in 1823 during the Trienio Liberal.
The Netherlands also employed Swiss mercenaries during the War of the Spanish Succession, hiring 11,200 men and deploying them for the Battle of Malplaquet (where rival Swiss regiments showed no quarter to each other). In 1715 and 1745, the Dutch Swiss regiments were sent to Scotland to help suppress Jacobite risings. By 1748, 20,400 Swiss soldiers were in Dutch service. Swiss units served as far afield as Ceylon, the Dutch East Indies, and South Africa, and 7,600 Swiss soldiers were still in Dutch service by World War I.
Savoy was another major employer, hiring several regiments during the Spanish succession war and employing 10,600 Swiss troops during the War of the Austrian Succession. It was not until 1832 that the King of Sardinia-Piedmont dismissed his Swiss bodyguard unit. Naples retained 6,000-7,000 Swiss troops in its service until they joined the French Army after the French Revolution, and the Swiss regiments remained in the Two Sicilies' army until 1859. Venice hired thousands of Swiss troops to fight in its wars with the Ottomans, with Swiss regiment fighting for the republic until 1719. Britain, Prussia, Poland-Lithuania, and other states also employed smaller numbers of Swiss troops.
Since 1859, the only Swiss mercenary unit permitted to exist has been the Pontifical Guard, 135 in number and all young, unmarried Swiss army veterans. In 1874, Switzerland otherwise banned the recruitment of its citizens as foreign mercenaries.