Messina Denaro was Italy’s number one fugitive, and he was arrested after 30 years on the run.
The head of the Carabinieri police force’s special operations squad said that Messina Denaro was captured on Monday at the clinic where he was receiving treatment for an undisclosed medical condition.
Messina Denaro was considered Sicily’s top Cosa Nostra boss even while he was a fugitive and was tried and sentenced to life in jail in absentia over numerous murders.
"This is a great victory for the state," said Italy's PM Giorgia Meloni.
The 60-year-old was taken to a secret location by police immediately after the arrest, Italian state television reported.
Messina Denaro was the last of three top-level Mafia bosses who had eluded capture for decades.
He was tried in absentia and convicted of dozens of murders, and now faces multiple life sentences.
Messina Denaro is set to be imprisoned for two bombings in Sicily in 1992 that murdered top anti-Mafia prosecutors Giovanni Falcone and Paolo Borsellino and the deadly 1993 bomb attacks in Milan, Florence and Rome.
Among other grisly crimes he was convicted of is the murder of a Mafia turncoat’s young son, who was strangled before his body was dissolved in a vat of acid.
The arrest on Monday came 30 years and a day after the capture of convicted “boss of bosses” Salvatore “Toto” Riina, in a Palermo apartment, after 23 years on the run.