John Joseph Gotti Jr. (/ˈɡɒti/ GOT-ee, Italian: [ˈɡɔtti]; October 27, 1940 – June 10, 2002) was an American mafioso and boss of the Gambino crime family in New York City. He ordered and helped to orchestrate the murder of Gambino boss Paul Castellano in December 1985 and took over the family shortly thereafter, leading what was described as the most powerful crime syndicate in the United States.

Gotti and his brothers grew up in poverty and turned to a life of crime at an early age. Gotti quickly became one of the Gambino family's biggest earners and a protégé of Aniello Dellacroce, the family's underboss, operating out of Ozone Park, Queens. Following the FBI's indictment of members of Gotti's crew for selling narcotics, Gotti began to fear that Castellano would kill him and his brother Gene for dealing drugs. As this fear continued to grow, and amidst growing dissent over the leadership of the family, Gotti arranged the murder of Castellano.

At his peak, Gotti was one of the most powerful and dangerous crime bosses in the United States. While his peers generally avoided attracting attention, especially from the media, Gotti became known as "the Dapper Don" for his expensive clothes and outspoken personality in front of news cameras. He was later given the nickname "the Teflon Don" after three high-profile trials in the 1980s resulted in acquittals, though it was later revealed that the trials had been tainted by jury tampering, juror misconduct and witness intimidation. Law enforcement continued gathering evidence against Gotti, who reportedly earned between $5 million and $20 million per year as Gambino boss.

Gotti's underboss, Salvatore "Sammy the Bull" Gravano, aided the FBI in convicting Gotti; in 1991, Gravano agreed to turn state's evidence and testify against Gotti after hearing the boss make disparaging remarks about him on a wiretap that implicated them both in several murders. In 1992, Gotti was convicted of five murders, conspiracy to commit murder, racketeering, obstruction of justice, tax evasion, illegal gambling, extortion and loansharking. He received life in prison without parole and was transferred to United States Penitentiary, Marion, in Illinois.

Gotti died of throat cancer on June 10, 2002, at the United States Medical Center for Federal Prisoners in Springfield, Missouri. According to Anthony "Gaspipe" Casso, the former underboss of the Lucchese crime family, "what John Gotti did was the beginning of the end of Cosa Nostra."

John Gotti was born in the Bronx borough of New York City on October 27, 1940. He was the fifth of the thirteen children (two had died at birth) of John Joseph Gotti Sr. and Philomena "Fannie" DeCarlo. Both of Gotti's parents were born in New York, but it is presumed that his grandparents were from San Giuseppe Vesuviano, in the Naples province of Southern Italy, because his parents were married and lived there for some time.

Gotti was one of five brothers who became made men in the Gambino crime family: Eugene "Gene" Gotti was initiated before John due to the latter's incarceration, Peter Gotti was initiated under John's leadership in 1988 and Richard V. Gotti was identified as a caporegime (captain, or head of a "crew") by 2002. The fifth, Vincent, was initiated in 2002.

By the time he reached the age of 12, John Gotti's family settled in East New York, Brooklyn, where he grew up in poverty alongside his brothers. His father worked irregularly as a day laborer. As an adult, Gotti came to resent his father for being unable to provide for his family. In school he had a history of truancy and bullying other students, and ultimately dropped out of Franklin K. Lane High School at the age of 16.