The World Series is the annual final championship series of Major League Baseball (MLB) in the United States and Canada. It has traditionally been held in October, though some more recent editions were contested in November due to expanded playoffs and/or season delays. It has been contested since 1903 between the champion teams of the American League (AL) and the National League (NL). The winner of the World Series championship is determined through a best-of-seven playoff, and the winning team is awarded the Commissioner's Trophy.

Major League Baseball (MLB) is a professional baseball league and the highest level of organized baseball in the United States and Canada. One of the big four major leagues, MLB comprises 30 teams, divided equally between the National League (NL) and the American League (AL), with 29 in the United States and 1 in Canada. Formed in 1876 and 1901, respectively, the NL and AL cemented their cooperation with the National Agreement in 1903, making MLB the oldest major professional sports league in the world. They remained legally separate entities until 2000, when they merged into a single organization led by the Commissioner of Baseball. MLB is headquartered in Midtown Manhattan.