A perfect season is any sports season, excluding 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 team sport, and has occurred more commonly at the collegiate level in the United States.
A perfect season may also be part of a multi-season winning streak.
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.