Overview
Thirty clubs across the American and National Leagues, 162 games each, and a best-of-seven World Series.
Major League Baseball is the premier professional baseball league in North America and one of the four major leagues in the United States and Canada. Thirty clubs — 29 in the US and one in Canada — are organised into the American League and the National League, each split into East, Central and West divisions.
Clubs play 162 games between late March and the end of September, followed by an expanded postseason: twelve teams qualify, the top two seeds in each league receive byes, and the survivors advance through best-of-three, best-of-five and best-of-seven rounds to the World Series.
Clubs
Every club in the league. Tap a name for its page.
American League
Season Format
Recent Champions
Most recent first. Seasons still in progress are marked.
History
The National League was founded in 1876 and the American League followed in 1901. A peace agreement between the two in 1903 created the framework of modern Major League Baseball and produced the first World Series that autumn; for most of the next century the leagues operated as separate organisations that met only in the World Series and the All-Star Game.
The colour line that had excluded Black players since the 1880s was broken in 1947 when Jackie Robinson debuted for the Brooklyn Dodgers — a landmark in American history as much as in the sport. The Negro Leagues that had operated in parallel were recognised as major leagues in 2020, and their statistics were incorporated into the official record in 2024.
Expansion took the league from sixteen clubs to thirty between 1961 and 1998, and in 2000 the two leagues were consolidated under a single commissioner's office. Recent seasons have been defined by rule changes aimed at pace and action: the pitch clock, bigger bases and limits on defensive shifts arrived in 2023, and an automated ball-strike challenge system in 2026.
Governance
MLB is led by the Commissioner of Baseball — Rob Manfred, the sport's tenth commissioner, in office since 2015 — and administered from the league office in New York. The 30 club owners govern collectively; players are represented by the Major League Baseball Players Association, historically the strongest union in American sport.
Internationally, baseball's world governing body is the WBSC, which sanctions the World Baseball Classic in partnership with MLB. Ongoing structural questions include the Athletics' move to Las Vegas, planned for 2028, and league discussion of expanding from 30 clubs to 32.