walter johnson
Mickey Mantle's longest hitting streak was 16 games.
Joe DiMaggio
20
Ichiro
Vladimir Guerrero had a 31 game hitting streak in 1999. While it was the longest streak for a season in the 90s it wasnt longest streak of the 90s. Hal Morris, Cincinnati Reds first baseman, had a 32 game hitting streak that started at the end of August of the 1996 season and carried over into the 1997 season.
Luis Gonzalez had a 30 game hitting streak from 04-11-1999 to 05-18-1998.
Robin Ventura
Miguel Cabrera
Joe DiMaggio at 56 games.
Joe DiMaggio
Joe Dimaggio. 56 games
The record is held by Joe DiMaggio with 56 games in 1941 However there may have been longer streaks in professional baseball, for example DiMaggio's 61 game hitting streak in the PCL back in his San Francisco Seals days.