A game seven is the final game of a best of seven series. This game can occur in the postseasons for Major League Baseball (MLB) (League Championship Series and World Series), the National Basketball Association (NBA) (all rounds of the NBA playoffs), and the National Hockey League (NHL) (all rounds of the Stanley Cup playoffs).
The game is generally played at the site of the team holding the home advantage across the series.
The nature of a best-of-seven series requires that the series be tied at three games apiece going into game seven, such that either team can take the series (advancing further in the playoffs or winning the championship) by winning the game. Because of this decisive nature, game sevens add an element of drama to their sports.
Aside from North American sports leagues, game sevens are also a fixture in many other sports around the world, mostly in baseball, basketball, and ice hockey leagues. Most codes of football do not employ a best-of-seven series (or any best-of-x series in general), hence game sevens are not played in those leagues.
Some playoff rounds (such as MLB's current Division Series) are played in a best of five format, such that game five has similar qualities to those described above, though the suspense and drama have less time to build in a shorter series. Furthermore, the World Series of 1903, 1919, 1920, and 1921 were played in a best of nine format, though none of the four went to a decisive game nine.