Arizona Diamondbacks (colloquially known as the D-backs) is an American professional baseball team based in Phoenix, Arizona. The Diamondbacks play in Major League Baseball (MLB) as a member club of the National League (NL) West Division. The franchise was formed as an expansion team and began play in 1998. The team plays its home games at Chase Field. In its fourth season,Arizona won the World Series championship, beating the New York Yankees in 2001, becoming the fastest expansion team in Major League history to win a championship.