The American Mafia,[8][9][10] commonly referred to in North America as the Italian-American Mafia, the Mafia, or the Mob,[8][9][10] is a highly organized Italian American crime related society and organized crime related group.

In North America, the organization is often colloquially referred to as the Italian Mafia or Italian Mob, though these terms may also apply to the separate yet related Sicilian Mafia or other organized crime groups in Italy, or ethnic Italian crime groups in other countries. The organization is often referred to by its members as Cosa Nostra (Italian pronunciation: [ˈkɔːza ˈnɔstra, ˈkɔːsa -], "our thing" or "this thing of ours") and by the American government as La Cosa Nostra (LCN). The organization's name is derived from the original Mafia or Cosa Nostra, the Sicilian Mafia, with "American Mafia" originally referring simply to Mafia groups from Sicily operating in the United States.

The Mafia in the United States emerged in impoverished Italian immigrant neighborhoods in New York's East Harlem (or "Italian Harlem"), the Lower East Side, and Brooklyn; also emerging in other areas of the Northeastern United States and several other major metropolitan areas (such as New Orleans[11] and Chicago) during the late 19th century and early 20th century, following waves of Italian immigration especially from Sicily and other regions of Southern Italy. Campanian, Calabrian and other Italian criminal groups in the United States, as well as independent Italian American criminals, eventually merged with Sicilian Mafiosi to create the modern pan-Italian Mafia in North America. Today, the Italian-American Mafia cooperates in various criminal activities with Italian organized crime groups, such as the Sicilian Mafia, the Camorra of Campania and the 'Ndrangheta of Calabria. The most important unit of the American Mafia is that of a "family", as the various criminal organizations that make up the Mafia are known. Despite the name of "family" to describe the various units, they are not familial groupings.[12]

The Mafia is currently most active in the Northeastern United States, with the heaviest activity in New York, Philadelphia, Baltimore, New Jersey, Pittsburgh, Buffalo, and New England, in areas such as Boston, Providence, and Hartford. It also remains heavily active in Chicago and has a significant and powerful presence in other Midwestern metropolitan areas such as Kansas City, Detroit, Milwaukee, Cleveland, and St. Louis. Outside of these areas, the Mafia is also very active in Florida, Phoenix, Las Vegas, and Los Angeles. Mafia families have previously existed to a greater extent and continue to exist to a lesser extent in Northeastern Pennsylvania, Dallas, Denver, New Orleans, Rochester, San Francisco, San Jose, Seattle, and Tampa. While some of the regional crime families in these areas may no longer exist to the same extent as before, descendants have continued to engage in criminal operations, while consolidation has occurred in other areas, with rackets being controlled by more powerful crime families from nearby cities.[13] At the Mafia's peak, there were at least 26 cities around the United States with Cosa Nostra families, with many more offshoots and associates in other cities. There are five main New York City Mafia families, known as the Five Families: the Gambino, Lucchese, Genovese, Bonanno, and Colombo families. The Italian-American Mafia has long dominated organized crime in the United States. Each crime family has its own territory and operates independently, while nationwide coordination is overseen by the Commission, which consists of the bosses of each of the strongest families. Though the majority of the Mafia's activities are contained to the Northeastern United States and Chicago, they continue to dominate organized crime in the United States, despite the increasing numbers of other crime groups.