The Arizona Diamondbacks, often shortened as the D-backs, are an American professional baseball team based in Phoenix, Arizona. They compete in Major League Baseball (MLB) as a member of the National League (NL) West division. The team plays its home games at Chase Field, formerly known as Bank One Ballpark. The Diamondbacks have won one World Series championship (defeating the New York Yankees in 2001) – becoming the fastest expansion team in Major League history to win a championship, which it did in only the fourth season since the franchise's inception.