This is a subject which has been disputed.
There are references stating that Ed Delahanty is the only player to win the MLB batting title in both leagues. He won the National League title in 1899 with a .410 average, but the dispute is regarding the 1902 title, where he batted .376 in the American League.
Other references have Delahanty's .376 batting average listed as second highest to Nap Lajoie's .378 in 1902.
In 1928, Goose Goslin of the Washington Senators won the A.L. Batting Title with a .379 average. The National League winner was Rogers Hornsby of the Boston Braves with a .387 average.
Al Kaline won the 1955 American League batting title with a .340 batting Average.
Hanley Ramirez won the 2009 National League Batting title with a .342 batting average, and Joe Mauer won the 2009 American League batting title with a .365 batting Average.
Ted Williams
Don Mattingly of the Yankees won the A.L. Batting title in 1984 with a .343 average.
Bill Madlock won the 1976 National League Batting title with a .339 batting average, and George Brett won the 1976 American League batting title with a .333 batting Average.
In 1876 Ross Barnes won the first National League batting title with a .429 batting average.
Joe Mauer won the 2009 American League batting title with a .365 batting Average.
In 1928, Goose Goslin of the Washington Senators won the A.L. Batting Title with a .379 average. The National League winner was Rogers Hornsby of the Boston Braves with a .387 average.
Tris Speaker won the title with a .386 batting average and was on the Cleveland Indians.
Al Kaline won the 1955 American League batting title with a .340 batting Average.
As of 2008, Nomar Garciaparra has won two batting titles. He won the 1999 American League batting title with .357 and the 2000 American League title with .372.
Hanley Ramirez won the 2009 National League Batting title with a .342 batting average, and Joe Mauer won the 2009 American League batting title with a .365 batting Average.
Derrek Lee of the Chicago Cubs won the league batting title with a .335 average.
Ted Williams
Chipper Jones won the 2008 National League Batting title with a .364 batting average, and Joe Mauer won the 2008 American League batting title with a .328 batting Average.
Don Mattingly of the Yankees won the A.L. Batting title in 1984 with a .343 average.