The 2015 NCAA Division I FBS football season was the highest level of college football competition in the United States organized by the National Collegiate Athletic Association (NCAA). The regular season began on September 3, 2015 and ended on December 12, 2015. The postseason concluded on January 11, 2016 with Alabama defeating Clemson in the 2016 College Football Playoff National Championship. This was the second season of the College Football Playoff (CFP) championship system.

The following rule changes have been made by the NCAA Football Rules Committee for the 2015 season:^[1]

• Eight-man officiating crews are made standard in FBS with the addition of the center judge position. Various FBS conferences experimented with eight-man crews in the 2013 and 2014 seasons.
• Unsportsmanlike conduct penalties of 15 yards will be called on players who pull or yank opponents off piles.
• A 10-second runoff and reset of the play clock to 40 seconds will occur if a defensive player's helmet comes off within the final minute of either half. Previously, the play clock was set to 25 seconds and no runoff occurred.
• The five-yard penalty for a first offense sideline warning has been removed, modifying a 2008 rule change. Moving forward, the second offense will be penalized five yards, followed by 15 yards (unsportsmanlike conduct) starting with the third offense.
• Officials will require players with illegal equipment (e.g., "crop-top" jerseys and writing messages on eye black) to leave the field for one play to correct it. Teams may use a time-out to correct the equipment and avoid the player having to sit out the play.
• Instant replay can be used to review if the kicking team blocked the receiving team before an onside kick has gone 10 yards.
• Teams must have 22 minutes for pre-game warmups, which can be shortened by mutual agreement of both teams.
• The play clock will be reset to 40 seconds if the play clock reaches 25 seconds before the ball is ready for play. Previously, the play clock was reset if the play clock ran to 20 seconds.
• Non-standard/overbuilt facemasks are prohibited.

A proposed rule to change the ineligible downfield rule from three yards to one yard past the line of scrimmage was tabled and not voted on; however it will be a point of emphasis for the season.

The use of advanced technology in games (e.g., wireless communication between on-field players and the bench, use of tablets by coaches for non-medical reasons, helmet cameras for players) is being studied by a committee for possible future implementation.

• June 1 – UAB, which had dropped football after the 2014 season, announced that it would reinstate it as early as 2016.^[4]
• July 21 – UAB announced that it had pushed back the return of football to the 2017 season.^[5]
• September 1 – The Sun Belt Conference announced that Coastal Carolina would become a full member of the conference on July 1, 2016. The Coastal Carolina football team, a member of the FCS Big South Conference along with the rest of the athletic program at the time of the announcement, began a transition to FBS after the 2015 season, joined Sun Belt football in 2017, and became fully bowl-eligible in 2018.^[6]
• January 13, 2016 – The NCAA Division I council approved a rule that, from the 2016 season forward, allows FBS conferences to stage championship games regardless of their current membership numbers. The new rule, as originally proposed by the Big 12 Conference and amended by the Big Ten Conference, stipulates that a conference with fewer than 12 members can stage a championship game under either of the following circumstances:^[7]
  • The game involves two division winners, with each division having played a round-robin schedule.
  • The game involves the top two teams in the conference standings after a full round-robin conference schedule.

Rankings reflect the AP Poll. Rankings for Week 10 and beyond will list College Football Playoff Rankings first and AP Poll second. Teams that fail to be a top 10 team for one poll or the other will be noted.

• Week 2
  • No. 5 Michigan State defeated No. 7 Oregon 31–28 (Spartan Stadium, East Lansing, Michigan)
• Week 7
  • No. 10 Alabama defeated No. 9 Texas A&M 41–23 (Kyle Field, College Station, Texas)
  • No. 6 LSU defeated No. 8 Florida 35–28 (Tiger Stadium, Baton Rouge, Louisiana)
• Week 10
  • No. 4/7 Alabama defeated No. 2/4 LSU 30–16 (Bryant-Denny Stadium, Tuscaloosa, Alabama)
• Week 12
  • No. 10/10 Baylor defeated No. 6/4 Oklahoma State 45–35 (Boone Pickens Stadium, Stillwater, Oklahoma)
  • No. 9/9 Michigan State defeated No. 3/2 Ohio State 17–14 (Ohio Stadium, Columbus, Ohio)
• Week 13
  • No. 3/5 Oklahoma defeated No. 11/9 Oklahoma State 58–23 (Boone Pickens Stadium, Stillwater, Oklahoma)
  • No. 8/8 Ohio State defeated No. 10/12 Michigan 42–13 (Michigan Stadium, Ann Arbor, Michigan)
  • No. 9/13 Stanford defeated No. 6/4 Notre Dame 38–36 (Stanford Stadium, Stanford, California)
• Week 14
  • No. 5/5 Michigan State defeated No. 4/4 Iowa 16–13 (Big 10 Championship Game, Indianapolis, Indiana)
  • No. 1/1 Clemson defeated No. 10/8 North Carolina 45–37 (ACC Championship Game, Charlotte, North Carolina)

No FBS programs opened new stadiums for the 2015 season. However, one school played its first season in FBS, and several other programs expanded or renovated their stadiums:

• Charlotte, playing its first season in FBS, debuted at the on-campus Jerry Richardson Stadium. The stadium opened for the 49ers' first season in 2013 with a capacity of 15,314, but was designed for quick expansion to as much as 40,000.
• Kentucky debuted a major renovation to Commonwealth Stadium. A$110 million project reduced the capacity from 67,530 to 61,000, and added a new recruiting plaza in the east end zone surrounded by a new student section, more than 20 new luxury boxes and 2,000 new club seats, new home-team facilities, a revamped exterior, and improved concourses.^[14]
• UCF took out about 2,000 seats from the east side of Bright House Networks Stadium, replacing them with a new club seating section with a capacity of about 1,000 that includes a beach area.^[15]
• Auburn debuted the largest video board in college football in Jordan–Hare Stadium. The video board measures 190 feet by 57. The project was expected to cost $13.9 million.
• Duke featured a newly renovated Wallace Wade Stadium. The renovations included removal of the track and lowering of the field by several feet; more seating capacity near field level along both sidelines and the north end zone; the replacement of bleachers on the west side of the stadium with Duke blue seats; new brick facades around much of the field; a brand-new, much larger video board and new speakers; a refresh of the concourse area around the top of the bowl, with new sidewalks and brick separating the concourse from the seating area; and new concession booths, restrooms, and concourse lighting along with a new elevator tower. Construction on a new press box, luxury boxes, and attached seats was ongoing throughout the season, and was expected to be complete in time for the 2016 season. These marked the first major upgrades to Wallace Wade Stadium in over 70 years.
• Kansas State debuted the Vanier Football Complex in the north end zone of Bill Snyder Family Stadium. This feature includes new seating, a video board, offices, locker rooms and strength training facilities. kstatesports.com
• Cincinnati debuted renovations to Nippert Stadium that increased the capacity to 40,000 and added premium seating, a new press box, a new pavilion, additional restrooms, upgraded concessions and improved concourses.
• Ole Miss announced plans to renovate Vaught–Hemingway Stadium during the 2015 season and the 2015–16 offseason. The project was intended to bring the stadium's ultimate capacity to 64,038. The stadium was to be turned into a complete bowl, adding club level seating, restrooms, concessions, etc. The renovation was planned for completion by the start of the 2016–17 season. This renovation was part of the Forward Together campaign, which also gave the Rebels a new basketball arena, The Pavilion at Ole Miss, right next to the football stadium.
• Texas A&M completed renovations to the west side and facade of Kyle Field, reducing the capacity from the previous season. The project cost over $450 million.

Rankings reflect the Week 14 AP Poll before the conference championship games were played.

This is restricted to coaching changes taking place on or after May 1, 2015. For coaching changes that occurred earlier in 2015, see 2014 NCAA Division I FBS end-of-season coaching changes.