Swiss Guards (French: Gardes Suisses; German: Schweizergarde) are the Swiss soldiers who have served as guards at foreign European courts since the late 15th century.
Foreign military service was outlawed by the revised Swiss Federal Constitution of 1874, with the only exception being the Pontifical Swiss Guard (Latin: Pontificia Cohors Helvetica, Cohors Pedestris Helvetiorum a Sacra Custodia Pontificis; Italian: Guardia Svizzera Pontificia) stationed in Vatican City. The modern Papal Swiss Guard serves as both a ceremonial unit and a bodyguard. Established in 1506, it is one of the oldest military units in the world.
The earliest Swiss guard unit to be established on a permanent basis was the Hundred Swiss (Cent Suisses), which served at the French court from 1490 to 1817. This small force was complemented in 1567 by a Swiss Guards regiment. In the 18th and early 19th centuries several other Swiss Guard units existed for periods in various European courts.
In addition to small household and palace units, Swiss mercenary regiments have served as regular line troops in various armies; notably those of France, Spain and Naples (see Swiss mercenaries). They were considered the most effective mercenaries of the 15th century until their battle-drill was improved upon by the German Landsknechte. At the Battle of Marignano (1515), the Landsknecht in French service defeated the Swiss pikemen.