World Series

The World Series is the annual championship series of Major League Baseball (MLB). It has been contested since 1903 between the champion teams of the American League (AL) and the National League (NL). The winning team, determined through a best-of-seven playoff (except in 1903 and from 1919–1921, when a best-of-nine format was used), is awarded the Commissioner's Trophy.

The series is traditionally played in October, although before expansion of the regular-season schedule from 154 to 162 games the event occasionally started in late September (most recently in 1955) and the entire 1918 series took place early in that month due to the World War I "Work or Fight" order forcing an early end to that year's regular season, while some more recent editions have been contested into November due to in-season delays and expansion of earlier postseason rounds. Because the series is played in the fall or autumn season in North America, it is often referred to as the Fall Classic.

Before the AL and NL were split into divisions in 1969, the team with the best regular-season win–loss record in each league won that league's pennant and advanced to the World Series, barring a tie necessitating a pennant playoff. Since 1969 each league has conducted a League Championship Series (ALCS and NLCS) preceding the World Series to determine which of its teams will advance, while those series have been preceded in turn by Division Series (ALDS and NLDS) since 1995, and Wild Card games or series in each league since 2012. Until 2002, home-field advantage in the World Series alternated from year to year between the AL and NL. From 2003 to 2016, home-field advantage was given to the league that won that year's All-Star Game. Starting in 2017, home-field advantage was awarded to the league champion team with the better regular-season win–loss record regardless of that team's seeding in earlier postseason rounds (i.e. a Wild Card team in one league will be given home-field advantage over a division winner in the other league if it had the better record or wins the tie-breaking procedure).

The World Series has been contested 121 times through 2025, with the AL team winning 68 times and the NL team 53.

Before 1882, when the American Association was formed as a second major league, the National Association of Professional Base Ball Players (1871–1875) and then the National League (founded 1876) represented the top level of organized baseball in the United States. All championships were awarded to the team with the best record at the end of the season, without a postseason series being played. From 1884 to 1890, the National League and the American Association faced each other in a series of games at the end of the season to determine an overall champion. These series were disorganized in comparison to the modern World Series, with the terms arranged through negotiation of the owners of the championship teams beforehand. The number of games played ranged from as few as three in 1884 (Providence defeated New York three games to zero), to a high of fifteen in 1887 (Detroit beat St. Louis ten games to five). Both the 1885 and 1890 Series ended in ties, each team having won three games with one tie game.

The series was promoted and referred to as "The Championship of the United States", "World's Championship Series", or "World's Series" for short. In his book Krakatoa: The Day the World Exploded: August 27, 1883, Simon Winchester mentions in passing that the World Series was named for the New York World newspaper, but this view is disputed.

The 19th-century competitions are not officially recognized as part of World Series history by Major League Baseball, which considers 19th-century baseball to be a prologue to the modern baseball era. As late as approximately 1960, some sources treated the 19th-century series on an equal basis with the post-19th-century series. After about 1930, however, many authorities date the modern World Series to 1903 and discuss the earlier contests separately. (For example, the 1929 World Almanac and Book of Facts lists "Baseball World's Championships 1884–1928" in a single table, while the 1943 edition lists "Baseball World's Championships 1903–1942".)

Following the collapse of the American Association after the 1891 season, the National League was again the only major league. The league championship was awarded in 1892 by a playoff between split season champions. This scheme was abandoned after one season. Beginning in 1893—and continuing until divisional play was introduced in 1969—the pennant was awarded to the first-place club in the standings at the end of the season. For four seasons, 1894–1897, the league champions played the runners-up in the postseason championship series called the Temple Cup. A second attempt at this format was the Chronicle-Telegraph Cup series, which was played only once, in 1900.