Annual championship of U.S. major league baseball, played between the top team of the American League (AL) and that of the National League (NL).
First held in 1903, it was canceled the following year after the New York Giants (NL) refused to play Boston (AL). The series resumed in 1905 and continued annually until a players' strike in 1994 forced its cancellation that year. A seven-game series has been standard since 1922.