Corleone mafia boss
Italian police said 73-year-old Provenzano, deemed the country's most wanted man, was arrested near his home town of Corleone in Sicily.
He was sentenced in his absence to life in prison for a string of murders.
Police believe he took over command of the Mafia after the 1993 arrest of ex-boss Salvatore "Toto" Riina.
Provenzano's capture is an important victory for law and order in Sicily, where the police still fight Mafia crime on a daily basis, says the BBC's David Willey in Rome.
Crimes he has been convicted of include the killings in 1992 of top anti-Mafia judges Giovanni Falcone and Paolo Borsellino.
Italian President Carlo Azeglio Ciampi expressed his delight over the arrest to Interior Minister Giuseppe Pisanu, a statement from the presidential palace said.
"His capture is an exceptionally important success because it makes it possible to hand over to justice the present head of Cosa Nostra [the Sicilian Mafia] and put an end to a flight that has lasted too long," Sicilian judges said in a joint statement.
Read more: bbc
