about: the championship series of Major League Baseball thumb|The Commissioner's Trophy from the Boston Red Sox's 2004 World Series win

The World Series is the championship series of Major League Baseball and the culmination of the Major League Baseball postseason each October. Since the Series takes place in mid-autumn, sportswriters many years ago dubbed the event the Fall Classic, a usage reflected in the logo for the 2008 World Series; it is also sometimes known as the October Classic or simply The Series. The reigning World Series Champions are the Philadelphia Phillies.

The World Series is played between the champion clubs of the American League and the National League, which collectively include (today) 29 clubs based in the United States and one club from Canada, whose rosters contain players from around the world. With the exception of 1904 (boycott) and 1994 (player strike), the "modern" World Series has been played as an annual event since 1903. Baseball has employed various championship formulas since the 1860s. When the term "World Series" is used by itself, it is usually understood to refer to the "modern" World Series exclusively.

The World Series championship is determined through a best-of-seven playoff. Best-of-seven has been the format of all the modern World Series except in 1903, 1919, 1920 and 1921 when the winner was determined through a best-of-nine playoff. The Series winner is awarded the World Series Trophy, as well as individual World Series rings. The Series winner also receives a larger proportion of the gate receipts than does the Series loser.

The New York Yankees of the American League have played in 39 of the 104 Series through 2008 and have won 26 World Series championships, the most of any Major League franchise and exactly one quarter of all World Series titles won to date. For the National League, the Dodgers have appeared in the Series the most at 18 times (9 each in Brooklyn and Los Angeles), but have won the Series only 6 times (once as Brooklyn, five times as Los Angeles). The St. Louis Cardinals have represented the National League 17 times and have won 10 championships, which is the second most for any National League team. The Chicago Cubs have the longest streak of not winning the World Series, with their last championship coming in 1908.List of World Series at Baseball Reference

Champions prior to and precursors to the modern World Series (1857–1902)

see: List of World Series#The original World Series

The original World Series

Until the formation of the American Association in 1882 as a second major league, the National Association and then the National League represented the top level of organized baseball in the United States. All championships went to whoever had the best record at the end of the season, without a postseason series being played. Starting in 1884 and going through 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 matchups were disorganized in comparison to the modern Series: games played ranged from as few as three in 1884 to a high of 15 in 1887 (Detroit beat St. Louis 10 games to 5), and both the 1885 and 1890 Series ended in ties, each team having won three games with one tie game.List of World Series at Baseball Reference