Which is the only NFL team to finish a season undefeated including playoffs?

The Miami Dolphins are the only NFL team to finish a season undefeated and untied, including the playoffs. Their 1972 team completed a perfect 17–0 season, a record that remains unmatched in NFL history.

Miami went 14–0 during the regular season under head coach Don Shula. The Dolphins then defeated the Cleveland Browns 20–14 in the divisional playoffs, beat the Pittsburgh Steelers 21–17 in the AFC Championship Game, and defeated Washington 14–7 in Super Bowl VII.

The achievement is especially remarkable because Miami used two starting quarterbacks during the season. Bob Griese broke his ankle in Week 5, so veteran Earl Morrall guided the team through the rest of the regular season. Griese returned during the conference championship game and started the Super Bowl.

The 2007 New England Patriots also reached the Super Bowl undefeated, but lost to the New York Giants and finished 18–1. The 1972 Dolphins therefore remain the only team to complete an entire NFL season without a loss or tie.