Joseph Dominick Pistone (born September 17, 1939) is an American former FBI agent who worked undercover as Donnie Brasco between September 1976 and July 1981, as part of an infiltration primarily into the Bonanno crime family under the tutelage of Anthony Mirra and later Dominick Napolitano, and to a lesser extent the Colombo crime family, two of the Five Families of the Mafia in New York City. Pistone was an FBI agent for 17 years, from 1969 until he resigned in 1986.
https://en.wikipedia.org/wiki/Joseph_D._Pistone