Organized crime in Italy and its criminal organizations have been prevalent in Italy, especially Southern Italy, for centuries and have affected the social and economic life of many Italian regions since at least the 19th century.

There are six major native mafia-like organizations that are heavily active in Italy. The oldest and most powerful of these organizations, having begun to develop between 1500 and 1800, are the 'Ndrangheta from Calabria (currently considered the most powerful criminal organization in the world), the Cosa Nostra from Sicily and the Camorra based in Campania. In addition to these three long-established organizations, there are also three other significantly active organized crime syndicates that were founded in the 20th century: the Stidda of Sicily, and the Sacra Corona Unita and Società foggiana, both from Apulia.

Four other Italian organized crime groups, namely the Banda della Magliana of Rome, the Mala del Brenta of Veneto, and the Banda della Comasina and Turatello Crew, both based in Milan, held considerable influence at the height of their power but are now severely weakened by Italian law enforcement or even considered defunct or inactive.

One other group, the Basilischi of Basilicata region, is currently active but is considered to have mostly fallen under the influence of the larger and more powerful 'Ndrangheta. Other crime groups include the Casamonica clan, a criminal organization of mostly Sinti ethnicity present in Rome and operating in the area of the Castelli Romani and the Lazio coast. The latest creation of Italian organized crime (IOC), Mafia Capitale (which was partially a successor or continuation of Banda della Magliana, involving many former Banda della Magliana members and associates) was mostly disbanded by the police in 2014.

The best-known Italian organized crime group is the Mafia or Sicilian Mafia (referred to as Cosa Nostra by members). As the original group named "Mafia", the Sicilian Mafia is the basis for the current colloquial usage of the term to refer to organized crime groups. It along with the Neapolitan Camorra and the Calabrian 'Ndrangheta are active throughout Italy, having presence also in other countries.

Mafia receipts may reach 9% of Italy's GDP. A 2009 report identified 610 comuni which have a strong Mafia presence, where 13 million Italians live and 14.6% of the Italian GDP is produced. The Calabrian 'Ndrangheta, as of 2022, the wealthiest and most powerful crime syndicate in Italy, accounts alone for over 3% of the country's GDP.

However, at 0.013 per 1,000 people, Italy has only the 47th highest murder rate compared to 61 countries and the 43rd highest number of rapes per 1,000 people compared to 64 countries in the world. These are relatively low figures among developed countries.