Smash Mouth Singer Steve Harwell's Ex-Fiancee Gets Restraining Order

Smash Mouth frontman Steve Harwell's former-fiancee claims he's been so abusive -- verbally and mentally -- that she needs court-ordered protection, and she got it ... TMZ has learned.

Esther Campbell filed new docs asking a judge to keep Harwell the hell away from her, after a series of alleged incidents she's blaming on his battle with substance abuse.

Esther claims Steve did a stint in rehab and seemed to be improving until early this year. In the docs, obtained by TMZ, she claims he fell off the wagon and had to detox in February, but when he got out of treatment ... Steve allegedly stole her phone and destroyed it. Esther also claims he stole her car keys to leave her car windows open in the rain.

She describes him as "vindictive, angry, vile and mean" ... according to the docs, and claims he's not taking his medication for bipolar disorder. We have not confirmed Harwell is bipolar, and he's never discussed it publicly.

As we first reported ... Campbell previously claimed Harwell was making her life a living hell with harassing texts, calls, emails and driving by her house.

The judge granted Esther a temporary restraining order which requires the singer to stop contacting her and stay 200-yards away.