The name commonly applied to a massacre conducted by the citizenry of Palermo on the island of Sicily, in 1282, killing hundreds of French administrators and officers who were stationed in the city. The massacre (which began at Vespers, evening church services, hence the name) was followed by many incidents across the island, bringing the death toll to more than 6000.
The reason for the massacre was widespread dissatisfaction with the harsh regime implemented by Charles I of Anjou, French ruler of Naples. The initially disorganised massacre soon developed into a full-blown insurrection, at the instigation of Peter III of Aragon, who conquered the island later that same year (although the island's new master was not formally acknowledged as such until 1302).
The events of the Sicilian Vespers form the basis of an opera, originally in French, by Giuseppe Verdi, Les Vêpres siciliennes (also known under the Italian title I Vespri Siciliani), first performed in Paris in 1855.