The National Collegiate Athletic Association (NCAA) Division I Football Bowl Subdivision (I FBS) includes 128 teams. Each team has one head coach. In addition to the head coach, most teams also have at least one offensive coordinator and defensive coordinator, however, the head coach will sometimes assume one of these roles as well. Division I FBS is composed of ten conferences: American Athletic Conference (The American), Atlantic Coast Conference (ACC), Big 12 Conference, Big Ten Conference, Conference USA (C-USA), Mid-American Conference (MAC), Mountain West Conference (MW), Pac-12 Conference (Pac-12), Southeastern Conference (SEC), and the Sun Belt Conference. As of the 2016 season, all FBS schools except four (Army, BYU, UMass, & Notre Dame) are members of one of these conferences.
As of the end of the 2015 season, following the retirement of Frank Beamer at Virginia Tech (who had been in that position since 1987), the longest-tenured head coaches in Division I FBS are Kirk Ferentz of Iowa and Bob Stoops of Oklahoma. Both began their current coaching tenures in 1999, and are also the only FBS head coaches who began their current head coaching positions before the 2000 season. Three other coaches hired after 2000 have a previous head coaching stint at their current school. Eighteen coaches took head coaching vacancies in the 2015 FBS season, and another 25 coaches have been hired to fill head coaching vacancies for the upcoming 2016 season.