List of pre-World Series baseball champions

The 1886 series between the St. Louis Browns of the American Association and the National League "Chicagos" was billed as a "World's Championship" with a winner-take-all prize of the total gate receipts.

The modern World Series, the current championship series of Major League Baseball (MLB) between teams of the National League and the American League, began in 1903, and was established as an annual event in 1905. This article discusses major-league champions before 1905, including championship series contested in that era, primarily between teams of the National League and the American Association.