The World Series, which since 1903 has been scheduled between the champion teams of the American League (AL) and the National League, is the Annual Major League Baseball Championship Series of both the United States and Canada (NL). The winner of the World Series Championship is decided by the best-of-seven playoffs, and the winning team is awarded the Commissioner's Cup.

Since the series is played in North America during the fall season, it is often referred to as the Fall Classic. Since 2017, it has been formally recognized as the World Series presented by YouTube TV for sponsorship purposes. Before the two teams being divided into divisions in 1969, the team with the better regular-season win-loss record in each league directly advanced to the World Series, barring a tie involving a pennant playoff.

There have been 116 World Series games so far, 66 of them have won the AL, and 50 the NL. The house-field advantage between the National League and the American League in the World Series was rotating year by year until 2002. The league that dominated the All-Star Game from 2003 to 2016 was awarded home-field advantage. The home advantage of the title team of the league with a superior record for winning every regular season was awarded beginning in 2017, even when all games for the 2020 season were hosted at a neutrally situated ballpark.

Why do they call the World Series winners World Champions and when did it start happening?

The alleged lack of rivalry from the globe led to North American media's longstanding, and contentious practice of using the phrase "World Champions." Today, in the United States, the sentence is more common but remains appropriate in Canada. Yet non-Americans typically ridicule this practice.

The usage of the term in baseball, which later became known as the World Series, begins with the organization of the National League and the earlier American Association championship series in the 1880s. The Major League Baseball later developed a four-year worldwide series dubbed The World Baseball Classic in order for a club to become a real World Champion.

In the 1950s, the recently founded NBA used the term "World Champions." The Super Bowl, the NFL-American Football League championship, has been specifically called after its first-round the World Championship Game.

In hockey, the Stanley Cup was originally open only to Canadian clubs, but in 1914, the Cup trustees allowed American teams to participate, with the requirement that the Stanley Cup winners would be recognized as World Champions. However, since 1976, in honor of the Stanley Cup winners, they have stopped calling the winners "World Champions", and have thus changed it to "Stanley Cup Champions".