2005 NCAA Division I-A football season

• *After the Big Ten Conference's 2004 experiment with instant replay, its use was expanded to all but the Sun Belt and the WAC conferences in Division I-A. The rules varied between conferences (including the use of coaches' challenges similar to the NFL in the Mountain West Conference) until the NCAA standardized the rules in 2006. Replay was also permitted in bowl games and, provided the visiting team agreed to its use, in non-conference regular season games.
• The protection for a receiver who signals a fair catch includes situations when the ball is muffed until it hits the ground.
• Penalties for spearing or similar hits in which the tackler leads with the crown of the head are enforced regardless of the "intent" of the tackler.
• The penalty for leaping on field goals/PATs now states it is a foul if a player lined up more than one yard behind the line of scrimmage jumps and lands on players of any team trying to block the kick. If lined up one yard or closer to the line, it is not a foul.
• Eliminated the "legal clipping zone"; hits from behind below the knee are prohibited anywhere on the field.
• Provided for officials a specific list of acts by players considered unsportsmanlike conduct, including the "throat slash", high stepping and diving into the end zone unchallenged among others. Spontaneous celebrations by players are allowed provided they are not prolonged, taunting, or bring attention to themselves.

A major conference realignment occurred prior to the 2005 season, when 18 teams in Division I-A changed conferences.

Temple was expelled from the Big East Conference while Army ended its brief affiliation with Conference USA, resulting in both schools becoming Independents.

Boston College left the Big East to become the 12th member of the Atlantic Coast Conference (ACC), allowing the league to split into two divisions and hold an annual championship game.

Cincinnati, Louisville and South Florida left Conference USA to join the Big East. Texas Christian University also left Conference USA to become the Mountain West Conference's ninth member.

Despite its losses, Conference USA added six schools to increase its membership to twelve, poaching Marshall and UCF from the Mid-American Conference and Rice, Southern Methodist, Tulsa, and UTEP from the Western Athletic Conference (WAC). Like the ACC, Conference USA split into two divisions and started a conference championship game.

The Western Athletic Conference added Idaho, New Mexico State and Utah State from the Sun Belt Conference.

The Sun Belt picked up I-AA Independents Florida Atlantic and Florida International.

Steve Spurrier as coach at the University of Florida

Steve Spurrier returned to college coaching for the first time since 2001 after a stint in the NFL, leading South Carolina to a respectable 7–5 season. Urban Meyer, after leading Utah to an undefeated season in 2004, took over at Florida (Spurrier's old school). Charlie Weis left the New England Patriots to become head coach at alma mater Notre Dame, taking the team to a BCS bowl.

Longtime head coaches Barry Alvarez of Wisconsin and Bill Snyder of Kansas State, both of whom took struggling programs to national prominence during their tenures, retired. Dan Hawkins, having helped make Boise State a powerhouse in the Western Athletic Conference, left the Broncos to coach struggling Colorado.

Rankings reflect the AP Poll. Rankings for Week 8 and beyond will list BCS Rankings first and AP Poll second. Teams that failed to be a top 10 team for one poll or the other will be noted.

• Week 2
  • No. 2 Texas defeated No. 4 Ohio State, 25–22 (Ohio Stadium, Columbus, Ohio)
• Week 3
  • No. 6 Florida defeated No. 5 Tennessee, 16–7 (Ben Hill Griffin Stadium, Gainesville, Florida)
• Week 4
  • No. 10 Tennessee defeated No. 4 LSU, 30–27 ^OT (Tiger Stadium, Baton Rouge, Louisiana)
• Week 6
  • No. 5 Georgia defeated No. 8 Tennessee, 27–14 (Neyland Stadium, Knoxville, Tennessee)
• Week 7
  • No. 1 USC defeated No. 9 Notre Dame, 34–31 (Notre Dame Stadium, South Bend, Indiana)
• Week 8
  • No. 2/2 Texas defeated No. 7/10 Texas Tech, 52–17 (Darrell K Royal–Texas Memorial Stadium, Austin, Texas)
• Week 10
  • No. 6/5 Miami defeated No. 3/3 Virginia Tech, 27–7 (Lane Stadium, Blacksburg, Virginia)
• Week 11
  • No. 7/5 LSU defeated No. 3/4 Alabama, 16–13 ^OT (Bryant-Denny Stadium, Tuscaloosa, Alabama)