Constantino Paul Castellano (1915-1985), better known as Paul Castellano, was a mafia boss in New York. Castellano belonged to the Gambino crime family, then one of New York's largest Mafia families, headed by Carlo Gambino. He was born in Brooklyn.

Castellano became boss after Carlo Gambino's death in 1976. While many people wanted the position as boss, it is suspected that Gambino appointed Castellano as his successor because Castellano was married to Gambino's sister and Gambino was a man who believed that family should come first. But Gambino decided at the same time to make Aniello Dellacroce his underboss, to prevent a street war from happening. After Gambino's death, Dellacroce became Castellano's underboss.

It is said that Castellano tried to run the organization like a company, and his connections expanded to places as far away as Kuwait. As part of an effort to lead a more open life-style, he purchased a large mansion in the prominent Todt Hill neighborhood of Staten Island.

From these changes, some of his captains apparently began to lose respect for his leadership, believing that Castellano had lost touch with the essence of the organization. Dellacroce, however, supposedly wouldn't approve of an attempt on his life, and thus they could not try to harm him.

On December 2, 1985, however, Dellacroce died of lung cancer. Within two weeks, on December 16, Castellano and his driver were shot to death outside Sparks Steak House in Manhattan, apparently on the orders of John Gotti, one of Castellano's captains in Queens. Controversy dogged Castellano even in death, as the Roman Catholic Archdiocese of New York refused to grant him the last rites of the church, citing the notorious circumstances surrounding both his life and death, leading many Italian-Americans (including New York State Governor Mario Cuomo) to accuse the predominantly Irish-American archdiocesan hierarchy of applying a prejudicial double standard (citing as an example the case of Brian O'Regan, an allegedly corrupt New York City police officer who, fearing impending arrest, committed suicide in a Long Island motel room the same year as Castellano's death; O'Regan did receive a Mass of Christian Burial despite the fact that a suicide note was found in the room and its authenticity was established beyond any doubt). Castellano was buried in Moravian Cemetery, a non-sectarian cemetery located in the New Dorp section of Staten Island.

Gotti succeeded Castellano as head of the Gambino family - a fact that was confirmed by the testimony of Sammy "The Bull" Gravano, a Gotti underboss, when he entered into a plea bargain with the government in 1990.