A perfect season is any sports season, including the playoff portion of a season, in which a team remains undefeated and untied. The feat is extremely rare at the professional level of any sporting competition, and has occurred more commonly at the collegiate level in the United States.
Since the NFL/AFL merger in 1970, only one team has played a complete perfect season (both playoff and regular season): the 1972 Miami Dolphins, who won their fourteen regular season games and three postseason games to finish 17-0.
The 2007 New England Patriots had the only other case of a perfect regular season, after winning their sixteen regular season games; however, they did not complete the perfect season, losing Super Bowl XLII to finish with a record of 18-1.
Preseason games are not counted toward standings, for or against. For example, the 1972 Miami Dolphins (mentioned below) lost three of their preseason games but still are considered to have a perfect season.
The 1972 Miami Dolphins won fourteen regular season games and three postseason games, including Super Bowl VII, to finish the season 17-0-0. They extended their winning streak the following season to 18 straight wins, until finally losing to the Oakland Raiders on September 23, 1973. It has often been reported that the surviving members of the 1972 Dolphins would gather to drink champagne when the final undefeated team earned its first loss, or that the team would send a case of champagne to the team that beat the final undefeated team. The head coach of the 1972 Dolphins, Don Shula, denied this in a 2007 interview with ESPN.
Prior to the development of a playoff system in the NFL in 1932, there were four teams who completed seasons undefeated, but with one or more tied games: the 1920 Akron Pros, the 1922 Canton Bulldogs, the 1923 Canton Bulldogs, and the 1929 Green Bay Packers. Under NFL practices at the time, tied games were discounted when the win percentage was calculated; so, these four teams were recorded with perfect win percentages of 1.000. (In 1972, the NFL retroactively altered its standings to treat tied games as being worth half of a win – so, these four teams are no longer recorded as having the perfect 1.000 percentage).
The 1921 Buffalo All-Americans were controversially denied a similar type of near-perfect season, when they believed that their final game, a 7-10 loss to the Chicago Staleys, was an exhibition game which would not count to the final standings; the NFL records that game as official, and Buffalo’s record as 9-1.
The 2007 New England Patriots were the first team to complete a perfect regular season since the length of the season was increased to sixteen games. They continued their success into the postseason before being beaten in Super Bowl XLII by the New York Giants, losing the perfect season by 3 points.
Before the modern NFL, American football was played professionally in a number of leagues, including an earlier version of the NFL. During this period, three teams completed perfect regular seasons: the 1934 Chicago Bears, the 1942 Chicago Bears, and the 1948 Cleveland Browns. Only the 1948 Browns had a true perfect season, but in the All-America Football Conference, not the NFL proper. AAFC records are not considered part of NFL history records, because not all of its teams entered the NFL.
The Bears are a member of the National Football League, which was founded in 1920 as the American Professional Football Association. In 1934, the Bears played to a 13-0-0 regular season record to become the first NFL team to complete an undefeated regular season without tied games. However, the Bears lost the 1934 NFL Championship Game against the New York Giants.
Despite losing several players and head coach George Halas to military service in World War II, the 1942 Bears played a perfect season, finishing 11-0-0. The Bears were again defeated in the NFL Championship Game, this time by the Washington Redskins.
The Browns were a member of the All-America Football Conference, a professional football league that played from 1946 to 1949. In 1948, the Browns won all fourteen regular season games and the 1948 AAFC championship to post a 15-0-0 record. Cleveland’s perfect 1948 season was part of a longer string of 29 straight wins, which stretched from 1947 to 1949 and included both the 1947 and 1948 title games. Overall, the Browns won all four AAFC championship games and were accepted into the NFL when the two leagues merged after the 1949 season.
The Los Angeles Bulldogs were a member of the second American Football League, who joined the league in 1937 after the Cleveland Rams defected to the NFL. Playing a combination of AFL teams and independent franchises (such as the Providence Steam Roller and the Salinas Packers), the team went 16-0, with 8 of those wins coming against AFL teams. The Bulldogs’ dominance is cited as one of the key factors in the AFL’s demise, and the next season (then as an independent, running up a 10-2-2 record including a 2-1-2 record against NFL teams), several of the team’s players were invited to play on the “Pro All Stars” team in the NFL’s first Pro All-Star Game, which was played in Los Angeles. The Bulldogs are considered to be one of the few independent teams to have ever achieved parity with the NFL.
Neither the NFL nor the Pro Football Hall of Fame recognizes the Bulldogs’ perfect season.
Since 1970, five NFL teams have had regular seasons with one loss: the 1976 Oakland Raiders (13-1) and the 1984 San Francisco 49ers, 1985 Chicago Bears, 1998 Minnesota Vikings, and 2004 Pittsburgh Steelers (all 15-1). The 1976 Raiders, 1984 49ers, and 1985 Bears all won three more games in the playoffs, including the Super Bowl; the ’76 Raiders finishing 16-1 and the ’84 49ers and ’85 Bears both 18-1. The 1998 Vikings and 2004 Steelers each won one playoff game before losing their respective conference championship games to finish 16-2. Most of these teams suffered their regular-season losses early in the year and never made what might be considered a serious run at a perfect season; only the 1985 Bears (12-0) were on track for a perfect season when they lost.
The best start from an NFL team who failed to complete a perfect regular season was by the 2009 Indianapolis Colts, who started 14-0 before losing their final two regular season games to the New York Jets and the Buffalo Bills (both former division rivals) respectively to finish 14-2. Indianapolis, having clinched the top seed in the AFC that year, sacrificed its chances at a perfect regular season and instead rested its starters the final two games to protect them for the playoffs. The Colts would go on to Super Bowl XLIV but lost to the New Orleans Saints.
Three other teams have started 13-0 before losing their fourteenth game: the 1998 Denver Broncos; the 2005 Indianapolis Colts and the 2009 New Orleans Saints.
There have been no perfect seasons in the American Association, World Football League, United States Football League, XFL, or, to date, the Arena Football League or United Football League.