Organized crime has far reaching economic, political, and social consequences. This entry presents the basic facts on the economics of mafias, with a special focus on the Sicilian case that may serve as a window into other types of criminal organizations. First, the entry provides a brief sketch of the theoretical modelling of the mafia. Then, it reviews the theoretical and empirical work testing the role of geography in the historical origins of the mafia. Finally, the entry explores the economic impact of the mafia in terms of missed opportunities of development, both in the short and in the long run. Different transmission channels are explored.