Leonardo "Narduzzo" Messina (born San Cataldo, September 22, 1955) is a Sicilian former mafioso who became a government informant or "pentito" in 1992. His testimony led to the arrest of over 200 mafiosi during the so-called "Operation Leopard" (Italian: Operazione Leopardo). Messina has implicated several politicians and government officials with ties to Sicilian Mafia, in particular Giulio Andreotti, seven times Prime Minister for Italy.

Born in San Cataldo, Caltanissetta, Messina was from a family of mafiosi going back a few generations. "I represent the seventh generation belonging to Cosa Nostra," he said. "I was affiliated not because I was a robber or because I was able to kill, but because I was bound to become a member by family tradition."

He left elementary school and became involved in burglary. He was imprisoned several times. In April 1982 after serving four years for armed robbery he eventually became a "man of honour" in the local Mafia family of San Cataldo. Messina became a close friend of Giuseppe Madonia, the boss of Vallelunga – one of the most important Mafia families in the province of Caltanissetta and an ally of the Corleonesi.

In 1984 he was arrested again for the killing of a drug dealer. He stayed in prison until 1989. After his release, he organized a drug trafficking ring for Giuseppe Madonia that covered several region in Italy. Madonia, in the meantime, had become the representative of the province of Caltanissetta in the Interprovincional Commission of Cosa Nostra.

Messina was arrested in April 1992 and decided to become a government informant (pentito). He was the first mafioso to start collaborating after the Capaci massacre in which judge Giovanni Falcone, his wife and three men of his police escort were killed. He said he was moved by emotional appeal of Rosaria Schifani – the widow of one of the police escorts of Falcone – against the Mafia.

Messina started to collaborate on June 30, 1992 and was a goldmine of information to Falcone’s colleague Paolo Borsellino, especially about the workings of the Mafia in central and southern Sicily. He talked about a rival mafia-like organisation in Sicily, the Stidda. It was composed originally of mafiosi who had left the organisation during the Second Mafia War of the 1981-82. The new group was particularly strong in southern Sicily around the towns of Agrigento, Caltanissetta and Gela. As a result of his declarations 203 arrest warrants were issued on November 17, 1992, in the so-called "Operation Leopard" (Operazione Leopardo). At that time the Mafia had killed Borsellino as well.

Messina also revealed that Cosa Nostra was in the midst of a profound internal crisis around 1990. Life within the organisation had become an intolerable nightmare under the reign of terror instituted by the Corleonesi under the leadership of Totò Riina. Murder had become institutionalised instead of a measure that had to be used sparingly and rationally.

Messina described how the Corleonesi organized their rise to power: "They took power by slowly, slowly killing everyone … We were kind of infatuated with them because we thought that getting rid of the old bosses we would become the new bosses. Some people killed their brother, others their cousin and so on, because they thought they would take their places. Instead, slowly, (the Corleonesi) gained control of the whole system. (…) First they used us to get rid of the old bosses, then they got rid of all those who raised their heads, like Giuseppe Greco 'the Shoe', Mario Prestifilippo and Vincenzo Puccio … all that’s left are men without character, who are their puppets."