The World Series is the annual championship series of Major League Baseball (MLB), played between the American League and National League champions since 1903. The winner of the World Series championship is determined through a best-of-seven playoff and awarded the Commissioner's Trophy. As the series is played in October, Major League Baseball also refers to it as the "Fall Classic". The most recent World Series was won by the St. Louis Cardinals, who defeated the Texas Rangers in 7 games in 2011.

The New York Yankees of the American League have played in 40 World Series and won 27, and the Oakland/Philadelphia Athletics have played in 14 and won 9. In the National League, the St. Louis Cardinals have played in 18 and won 11, while the San Francisco/New York Giants and Los Angeles/Brooklyn Dodgers have both appeared in 18 and won 6.

Until the formation of the American Association in 1882 as a second major league, the National Association of Professional Base Ball Players (1871–75) and then the National League (founded 1876) 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 (Providence defeated New York 3 games to zero), 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.

Koji Uehara (上原 浩治, Uehara Kōji^?, born April 3, 1975, in Neyagawa, Osaka, Japan) is a Japanese Major League Baseball right-handed relief pitcher. He is currently a relief pitcher for the Texas Rangers.

Uehara throws a high-80s four-seam fastball (tops out at 92 mph) and a solid forkball as his primary pitches. He's never been a power pitcher anywhere, but still has a great K/BB ratio with his pinpoint command.

Uehara graduated from the Osaka University of Health and Sport Sciences, and was drafted with the first pick by the Yomiuri Giants in 1998. He had a successful rookie year in 1999, with 15 consecutive wins which broke the all-time rookie record, claimed the Rookie of the Year, Eiji Sawamura Award, and led in wins, ERA, strikeouts and winning percentage.

In 2001, he finished with a 4.02 ERA, the highest of his career. However, in 2002, he rebounded, leading the Central League in wins and collected his second Sawamura Award.

He was injured before the 2007 season which made him a late appearance, and in that season, he became a closer instead, recorded an 1.74 ERA with 4 wins, 3 losses and 32 saves. Though showing a good ability both starting and closing, he returned as a starting pitcher in the 2008 season. He left the Giants after that season becoming a free agent and allowing him to play in Major League Baseball.