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.

Valon Behrami (born 19 April 1985) is a Swiss footballer who plays as a midfielder for Fiorentina. His previous clubs include Stabio, Chiasso, Lugano, Genoa, Verona, Lazio and West Ham United. Behrami has been capped at international level by the Switzerland national team. He was born in Mitrovica, Kosovo, then a part of the Socialist Federal Republic of Yugoslavia, and emigrated to Switzerland as a child with his parents.

Behrami was born in Titova Mitrovica, Yugoslavia (Kosovo) to Kosovan-Albanian parents. When Behrami was five, his parents both lost their jobs; his mother Halime as a secretary and his father Ragip as a manager of a plastics company. As a result, Behrami along with his parents and older sister Valentina moved to Stabio, a village in the Italian-speaking part of Switzerland. Behrami's mother described him as energetic: "As a child, running was Valon's favourite pastime – he just never got tired. Even now, he can hardly sit still for a second. He always needs a ball at his feet."

Mark William Calaway (born March 24, 1965) is an American professional wrestler better known by his ring name The Undertaker. He is signed to WWE and is the company's most tenured competitor. Calaway began his wrestling career with World Class Championship Wrestling (WCCW) in 1984. He joined World Championship Wrestling (WCW) as "Mean" Mark Callous in 1989. When WCW did not renew Calaway's contract in 1990, he signed with the World Wrestling Federation in October and, after shortening his name from Kane the Undertaker to simply The Undertaker, has remained with the company since.

The Undertaker has two contrasting personas. The first is the role of The Deadman, an undead, occult-like figure, which has consisted of many different styles. He debuted his original Deadman persona during his own on-camera debut at Survivor Series (1990). At this event, the Undertaker was clad as a Western mortician. Next, in October of 1998, the Undertaker appeared as the leader of the Ministry of Darkness (with similar apparel). Since WrestleMania XX, the Undertaker has appeared as a hybrid version of the Deadman character, using elements of the previous Deadman incarnations.