Jack White's Estranged Wife -- He Scares Me ... I Need a Restraining Order

Jack White -- lead singer of the White Stripes -- has been hit with a restraining order ... after his estranged wife told a judge she fears the rocker is DANGEROUS and could cause her harm.

Karen Elson obtained the restraining order in Tennessee in July -- claiming White has an explosive and violent temper ... and has berated her in emails loaded with profanity.

In the legal docs, Elson -- a model and singer -- says she fears for her own safety ... AND the safety of the couple's two young children.

Jack and Karen were married in 2005 in a canoe in the middle of the Amazon river in Brazil ... only to separate in 2011. Karen finally filed for divorce in 2012.