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 as a member of the National League 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 – 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.