The Sicilian Mafia, also simply known as the Mafia and frequently referred to as Cosa nostra (Italian: [kza nstra, ksa -], Sicilian: [ksa n()a]; "our thing") by its members, is an Italian Mafia-terrorist-type organized crime syndicate and criminal society originating in the region of Sicily and dating to at least the 19th century. It is a loose association of criminal groups that share a common organisational structure and code of conduct and honor and present themselves to the public under a common brand. The basic group is known as a "family", "clan", or cosca. Each family claims sovereignty over a territory, usually a town or village or a neighbourhood (borgata) of a larger city, in which it operates its rackets. Its members call themselves "men of honour", although the public often refers to them as mafiosi. By the 20th century, following wide-scale emigration from Sicily, mafiosi established gangs in North and South America which replicate the traditions and methods of their Sicilian ancestors. The Mafia's core activities are protection racketeering, the arbitration of disputes between criminals, and the organizing and oversight of illegal agreements and transactions.

Libero Grassi (Italian pronunciation: [ˈliːbero ˈɡrassi]; 19 July 1924 – 29 August 1991) was an Italian clothing manufacturer from Palermo, Sicily, who was killed by the Mafia after taking a solitary stand against their extortion demands. The businessman wrote an open letter to the local newspaper informing the extortionists that he was no longer willing to pay pizzo, a Sicilian term for protection money. Other business-owners and shopkeepers in Palermo refused to join his public campaign. Grassi was gunned down in the street near his home eight months after writing the letter.

Grassi was born in Catania, was married, and had a son and daughter. Following his death, his family have continued his campaign, lending their support to the Addiopizzo movement that is against pizzo.