William Stephen Belichick (; born April 16, 1952) is an American sports analyst and American football coach. Widely regarded as one of the greatest head coaches of all time, he holds numerous coaching records, including the record of most Super Bowl wins (six) as a head coach, all with the New England Patriots, along with two more during his time as the defensive coordinator of the New York Giants, for a record eight combined total Super Bowl victories as coach and coordinator. A renowned American football historian, Belichick is often referred to as a "student of the game" with a deep knowledge of the intricacies of each player position. During his tenure with the Patriots, Belichick was a central figure as the head coach and de facto general manager during the franchise's dynasty from 2001 to 2019.

Belichick is a descendant of the Bill Parcells coaching tree. He began his coaching career in 1975 as an assistant for the Baltimore Colts and became the defensive coordinator for New York Giants head coach Bill Parcells by 1985. Parcells and Belichick won two Super Bowls together before Belichick left to become the head coach of the Cleveland Browns in 1991. He remained in Cleveland for five seasons but was fired following the team's 1995 season. Belichick rejoined Parcells, first in New England where the team lost Super Bowl XXXI, and later with the New York Jets. After being named head coach of the Jets, Belichick resigned after only one day on the job to accept the head coaching job for the Patriots on January 27, 2000. In 24 seasons under Belichick, the Patriots won 17 AFC East division titles, made 13 appearances in the AFC Championship Game, and appeared in nine Super Bowls, with a record six wins. Overall, Belichick has won eight Super Bowl titles (the most of any individual in NFL history) and finished as runner-up four times from his combined time as an assistant and head coach.

At the time Belichick left the Patriots, he was the NFL's longest-tenured active head coach. Belichick has the most playoff coaching wins all-time with 31 and ranks third in regular season coaching wins in the NFL with 302. He is also in second place for combined regular season and postseason wins, and also second place for most regular season coaching wins with one franchise. Belichick is one of only three head coaches who have won six NFL titles. He was named the AP NFL Coach of the Year for the 2003, 2007, and 2010 seasons. Belichick has also been selected to the NFL 2000s All-Decade Team, NFL 2010s All-Decade Team, as well as the NFL 100th Anniversary All-Time Team, and is the only active head coach on the latter team.