Matteo Messina Denaro (Italian pronunciation: [matˈtɛːo mesˈsiːna deˈnaːro]; Sicilian: Matteu Missina Dinaru; born 26 April 1962), also known as Diabolik (from an Italian comic book character), is a Sicilian Mafia boss from Castelvetrano. He was considered to be one of the new leaders of the Sicilian mob after the arrests of Bernardo Provenzano on 11 April 2006 and Salvatore Lo Piccolo in November 2007. The son of a Mafia boss, Denaro became known nationally on 12 April 2001 when the magazine L'Espresso put him on the cover with the headline: Ecco il nuovo capo della Mafia ("Here is the new Mafia boss").

Messina Denaro became a fugitive on the most wanted list in 1993; according to Forbes in 2010, he was one of the ten most wanted and powerful criminals in the world. With the deaths of Bernardo Provenzano in 2016 and Salvatore Riina in 2017, Messina Denaro was seen as the unchallenged boss of all bosses within the Mafia. After 30 years on the run, he was arrested on 16 January 2023 near a private clinic in Sicily's capital, Palermo.