Bill Parcells (born August 22, 1941), nicknamed "The Big Tuna", is an American football head coach.

He received his first head coaching job in the National Football League with the New York Giants in 1983. After a dismal first season at 3-12-1, Parcells proceeded to take the New York Giants to the Super Bowl on two separate occasions. The first was in 1986, where he won against the Denver Broncos in Super Bowl XXI and the second was in 1990 where he won against the Buffalo Bills in Super Bowl XXV. He retired from football after that season due to health problems. From 1991 through 1992, he spent as a football analyst for NBC Sports.

After a three-year hiatus, Parcells returned as a coach for the struggling New England Patriots. Within two years, Parcells coached the team to a 10-6 record and its first playoff game in eight years. In 1996, he guided the Patriots to Super Bowl XXXI but lost to the Green Bay Packers. In the following year, Parcells took the New York Jets head coach vacancy which like New England had several losing seasons before he took over. In his first season with the Jets, the team barely missed the playoffs with a record of 9-7. In the 1998 football season, the Jets went to the playoffs with a 12-4 record but lost to the eventual Super Bowl-champion Denver Broncos in the AFC Championship Game. In 1999, Bill Parcells retired from football again, vowing that he will not coach again.

However, following three straight 5-11 losing seasons, Dallas Cowboys' owner Jerry Jones lured Bill Parcells out of retirement and made him the head coach in 2003. In his first season with the Cowboys, they went to the playoffs with a 10-6 record. Bill Parcells is the first head coach in the history of the NFL to guide four different teams to the playoffs.