The 2005 NASCAR Nextel Cup Series was the 57th season of professional stock car racing in the United States and the 34th modern-era Cup series. The season began on Saturday, February 12. The ten-race Chase for the Nextel Cup started with the Sylvania 300 on Sunday, September 18, and ended on Sunday, November 20, with the Ford 400.

Tony Stewart was the dominant driver going into the ten race "playoff" with five wins. Going into the final race before the Chase for the Nextel Cup, Stewart had amassed a 209-point lead over his nearest competitor, Greg Biffle. Points are reset going into the Chase for the cup, and Stewart's lead was dropped to a 5-point margin. Leading into the final race before the Chase, ten racers were still mathematically contending for the final four spots in the Chase and only one point separated Jamie McMurray in 10th from Ryan Newman in 11th. In the end, the ten racers who qualified for the Chase for the Cup were:

Tony Stewart (3716) Greg Biffle (−185) Rusty Wallace (−304) Jimmie Johnson (−316) Kurt Busch (−412) Mark Martin (−443) Jeremy Mayfield (−488) Carl Edwards (−602) Matt Kenseth (−602) Ryan Newman (−661)

Overall, Roush Racing was the dominant team going into the Chase for the Cup with five of the ten final racers from their organization (Biffle, Busch, Martin, Edwards, and Kenseth).

This was the first season since his rookie season that Jeff Gordon did not finish in the top 10 in points. The 2005 season was the only time Jeff Gordon failed to qualify for the Chase and one of only two seasons (alongside 1993) in which he did not finish in the top 10 in points.

The 2005 season was the first year of competition for the Dodge Charger since 1977, which replaced the Dodge Intrepid, a model that Dodge dropped from its consumer lineup for the 2005 model year. The change did little to improve Dodge's fortunes as a distant third manufacturer in NASCAR Nextel Cup behind Ford and Chevrolet. In 2004, Dodge won 4 of 36 cup races with the Intrepid. In 2005, the Charger won three races. The Charger was, however, much more of a success in the Busch Series, winning 10 of 32.

The 2005 season was the final year for the Ford Taurus, which was replaced by the Ford Fusion in the 2006 season. In addition, two prominent drivers announced that this would be their final season in NASCAR: Mark Martin, and 1989 Winston Cup Champion Rusty Wallace. Wallace would stay with his word and retire at season's end, but Martin, however, would return for 2006 due to circumstances with Roush Racing and Kurt Busch at the end of 2005. He would then run a limited schedule in 2007 and 2008, then drive full-time Hendrick Motorsports between 2009 and 2011, picking up an additional 5 wins with the team, and then finally run part-time again before officially retiring at the end of the 2013 season. Also, Ricky Rudd took a break after the 2005 season but returned at the beginning of 2007.

One of the biggest controversies prior to the start of the season involved the elimination of two races – Darlington and North Carolina Speedway in Rockingham. The eliminated Rockingham race ends NASCAR's 38-year association with Rockingham. The races were replaced by new races at Texas and Phoenix. NASCAR also began moving start times later in the day starting this season; by 2007 the Daytona 500 finished in primetime.

Also, NASCAR announced in January 2005 that the owners of the teams in the top 35 of the previous year's standings would be guaranteed a starting spot in each of the first five races of the season. This further complicated the unique qualifying procedure for the Daytona 500 and severely affected the chances of some teams to make races after having a poor 2004. After the fifth race, the guaranteed starters were based on the current season's points, with changes possible from race to race depending on results.

The number of cars entered for each race was up slightly from the previous year. The Daytona 500 saw a dramatic increase in its car count from 45 to 56. The increase was in part attributable to a new NASCAR rule that allowed hard liquor brands to become sponsors on its race cars. Roush Racing (Crown Royal), Richard Childress Racing (Jack Daniels), and Robby Gordon Motorsports (Jim Beam) were the first to sign such deals.

At the end of the 2005 season, Chevrolet won the NASCAR Manufacturers' Championship after winning 17 events and garnering 259 points over second-place Ford who captured 16 victories and 246 points.

Teams and drivers Complete schedule Manufacturer Team Drivers Crew Chiefs Chevrolet Dale Earnhardt, Inc. 8 Dale Earnhardt Jr. Pete Rondeau Steve Hmiel Tony Eury Jr. 15 Michael Waltrip Tony Eury Jr. Tony Gibson Front Row Motorsports 92 Stanton Barrett (R) Fred Wanke Tony Raines Hermie Sadler Eric McClure (R) Kenny Wallace Johnny Miller Joey McCarthy Mike Skinner P. J. Jones Chad Chaffin Haas CNC Racing 0 Mike Bliss Bootie Barker Hendrick Motorsports 5 Kyle Busch (R) Alan Gustafson 24 Jeff Gordon Robbie Loomis Steve Letarte 25 Brian Vickers Lance McGrew 48 Jimmie Johnson Chad Knaus Joe Gibbs Racing 11 Jason Leffler Dave Rogers Mike Ford Terry Labonte J. J. Yeley Denny Hamlin 18 Bobby Labonte Steve Addington 20 Tony Stewart Greg Zipadelli MB2 Motorsports 01 Joe Nemechek Ryan Pemberton MBV Motorsports 10 Scott Riggs Doug Randolph Morgan-McClure Motorsports 4 Mike Wallace Chris Carrier P. J. Jones John Andretti Todd Bodine PPI Motorsports 32 Bobby Hamilton Jr. Harold Holly Ron Fellows Richard Childress Racing 07 Dave Blaney Phillipe Lopez 29 Kevin Harvick Todd Berrier 31 Jeff Burton Kevin Hamlin Robby Gordon Motorsports 7 Robby Gordon Bob Temple Dodge BAM Racing 49 Ken Schrader David Hyder Bill Davis Racing 22 Scott Wimmer Derrick Finley Chip Ganassi Racingwith Felix Sabates 40 Sterling Marlin Steve Boyer Scott Pruett 41 Casey Mears Jimmy Elledge 42 Jamie McMurray Donnie Wingo Evernham Motorsports 9 Kasey Kahne Tommy Baldwin Jr. 19 Jeremy Mayfield Kenny Francis Penske-Jasper Racing 2 Rusty Wallace Larry Carter 12 Ryan Newman Matt Borland 77 Travis Kvapil (R) Shane Wilson Petty Enterprises 43 Jeff Green Greg Steadman 45 Kyle Petty Paul Andrews R&J Racing 37 Kevin Lepage Billy Poindexter Anthony Lazzaro Tony Raines Mike Garvey Jimmy Spencer Mike Skinner Ford Peak Fitness Racing 66 Hermie Sadler James Ince Mike Garvey Johnny Borneman III Jimmy Spencer Kevin Lepage Robert Yates Racing 38 Elliott Sadler Todd Parrott Kevin Buskirk 88 Dale Jarrett Mike Ford Bill Wilburn Todd Parrott Roush Racing 6 Mark Martin Pat Tryson 16 Greg Biffle Doug Richert 17 Matt Kenseth Robbie Reiser 97 Kurt Busch Jimmy Fennig Kenny Wallace 99 Carl Edwards (R) Bob Osborne Wood Brothers Racing 21 Ricky Rudd Michael McSwain

Limited schedule ManufacturerTeamDriver(s)Crew ChiefRoundsChevrolet Braun Racing08 Shane Hmiel Keith Montgomery McGlynn Racing Ryan McGlynn Derrike Cope Conely Racing79 Stan Boyd Derrike Cope Bryan Reffner Competitive Edge Motorsports51 Stuart Kirby Bob Schacht Bryan Reffner Mike Garvey Dale Earnhardt, Inc.1 Martin Truex Jr. Pete Rondeau Paul Menard Furniture Row Racing78 Kenny Wallace Tim Weiss Joe Garone Jerry Robertson Hendrick Motorsports 44 Terry Labonte Peter Sospenzo MB Sutton Motorsports 36 Boris Said Frank StoddardMach 1 Motorsports34 Randy LaJoie Mike Steurer Steve Portenga Jeff Fuller P. J. Jones Joey McCarthy Ted Christopher Eric McClure (R) Chad Chaffin NEMCO Motorsports 87 Chris Cook Gary Putnam Raabe Racing Enterprises 73 Eric McClure (R) Tim Brewer Richard Childress Racing 33 Kerry EarnhardtGil Martin Clint Bowyer Brian Simo Stanton Barrett Motorsports 95 Stanton Barrett David Ifft Mike Dayton S.W.A.T. Racing 55 Derrike Cope DodgeArnold Motorsports50 Jimmy Spencer Buddy Sisco Jorge Goeters Bill Davis Racing 23 Mike SkinnerDoug Wolcott Johnny Benson Bobby Hamilton Racing 04 Bobby Hamilton Danny Rollins Buddy Sisco Racing 61 Jeff Fuller Tony Raines Wayne Anderson Chip Ganassi Racingwith Felix Sabates39 Bill Elliott Lee McCall Scott Pruett David Stremme Reed Sorenson Evernham Motorsports 91 Bill Elliott Chris Andrews GIC-Mixon Motorsports 93 Geoff Bodine Lee McCall Phoenix Racing09 Johnny SauterTony Liberati Ralph Wingfield Marc Reno Joe Shear Jr. Bobby Hamilton Reed Sorenson Rick Ware Racing52 Larry GunselmanRick Ware Derrike Cope José Luis Ramírez Sacks Motorsports 13 Greg Sacks Paul Sacks Shepherd Racing Ventures89 Morgan Shepherd Troy Kelly Jason Jarrett Zero Four Motorsports75 Wayne AndersonBarry Haefele Mike Garvey FordKirk Shelmerdine Racing27 Kirk ShelmerdinePhil Harris Brad Teague Tom Hubert Ted Christopher ppc Racing 14 John Andretti Dave Charpentier ChevroletDodgeFordMichael Waltrip Racing00 David ReutimannGere Kennon Dom Turse Ryan McGlynn Jeff Spraker Terry Wooten Dennis Fieble Butch Hylton Johnny Benson Kenny Wallace Bill Davis Racing Mach 1 Motorsports Mike Skinner McGlynn Racing Carl Long Derrike Cope 80Carl LongStan Hover Dom Turse Dennis Fieble Hover Motorsports Andy Belmont Joe Gibbs Racing J. J. Yeley DodgeFord Ash Motorsports 02 Brandon Ash Ed Ash

Driver changes Mike Bliss drove full-time with Haas CNC Racing after competing in the final two races for Haas in 2004. Robby Gordon left Richard Childress Racing to drive for his own team Robby Gordon Motorsports. Jeff Burton moved over to the No. 31 after competing in the last fourteen races in the No. 30 for Richard Childress Racing. Travis Kvapil drove full-time with Penske-Jasper Racing after driving their R&D car in four of the last five races in 2004. Kyle Busch and Terry Labonte swapped seats with Hendrick Motorsports. Busch drove the No. 5 and Labonte drove the No. 44 R&D car on a part-time schedule. Jason Leffler joined Joe Gibbs Racing in 2005. Mike Wallace drove full-time with Morgan-McClure Motorsports after competing in the final two races for them in 2004. Dave Blaney moved over to the No. 07 after competing in eight races in the No. 30 for Richard Childress Racing in 2004. Bobby Hamilton Jr. drove full-time with PPI Motorsports after competing in eleven races in 2004.

Team changes Front Row Motorsports will run a full-time schedule as the No. 92. Kirk Shelmerdine Racing will run a part-time schedule. Michael Waltrip Racing, Bill Davis Racing, Mach 1 Motorsports and McGlynn Racing formed an alliance to run the No. 00. MB Sutton Motorsports ran the No. 36 rather than MB2 Motorsports. R&J Racing will run a full-time schedule as the No. 37.

Schedule