Major League Baseball was a professional baseball organization on Earth during that planet's 20th and 21st centuries. It oversaw the planet's most renowned professional baseball teams, including the Chicago Cubs, the New York Yankees, and the London Kings. (DS9: "Emissary", "If Wishes Were Horses"; DS9 Season 1 production art)
The organization presided over the yearly championship games known as the World Series from 1903 through 2042. (DS9: "If Wishes Were Horses", "Distant Voices"; VOY: "One Small Step") Sometime during the 21st century, Major League Baseball divided into the Planetary Baseball League, expanding their operation from the United States of America to the rest of the world. (DS9 Season 1 production art)