Salvatore "Sammy the Bull" Gravano is an American former mobster who rose to the position of underboss in the Gambino crime family. As the underboss, Gravano played a major role in prosecuting John Gotti, the crime family's boss, by agreeing to testify as a government witness against him and other mobsters in a deal in which he confessed to involvement in 19 murders.

The Gambino crime family is an Italian-American Mafia crime family and one of the "Five Families" that dominate organized crime activities in New York City, within the nationwide criminal phenomenon known as the American Mafia. The group, which went through five bosses between 1910 and 1957, is named after Carlo Gambino, boss of the family at the time of the McClellan hearings in 1963, when the structure of organized crime first gained public attention. The group's operations extend from New York and the eastern seaboard to California. Its illicit activities include labor and construction racketeering, gambling, loansharking, extortion, money laundering, prostitution, fraud, hijacking, and fencing.