MLB
The top professional baseball league in the United States and Canada — 30 clubs across the American and National Leagues, competing each season for the World Series.
Overview
Major League Baseball (MLB) is the premier professional baseball league in North America and one of the major professional sports leagues in the United States and Canada. It is made up of 30 clubs — 29 in the U.S. and one in Canada — organized into two leagues, the American League (AL) and the National League (NL), each split into East, Central and West divisions.
Clubs play a long regular season followed by an expanded postseason that culminates in the World Series, a best-of-seven championship between the AL and NL pennant winners. MLB traces its modern structure to the early 1900s and today operates under a single Commissioner's Office.
Leagues & Divisions
Season Format
Recent World Series Champions
History
Organized major-league baseball in the United States dates to the founding of the National League in 1876, joined by the American League in 1901. A 1903 agreement between the two leagues established the framework of modern MLB and produced the first World Series that autumn. For decades the two leagues operated as separate organizations that met only in the World Series and the All-Star Game.
The sport integrated in 1947 when Jackie Robinson debuted, a landmark moment in both baseball and American history. The league expanded steadily through the second half of the twentieth century to reach 30 clubs by 1998, and in 2000 the AL and NL were consolidated under a single Commissioner's Office.
Governance
MLB is led by the Commissioner of Baseball — currently Rob Manfred, the sport's 10th commissioner, in office since 2015 — and administered from the league office in New York City. The 30 club owners govern collectively, while players are represented by the Major League Baseball Players Association (MLBPA). Internationally, baseball's world governing body is the WBSC; MLB sits within its Americas region.
Recent and upcoming changes reflect the league's ongoing evolution: pace-of-play rules including the pitch clock, an automated ball-strike challenge system arriving in 2026, the Athletics' planned move to Las Vegas in 2028, and league discussion of expanding from 30 to 32 clubs.