Stefano Langone -- the "American Idol" contestant who showed his massive scars -- was the victim of a drunk driving accident in 2009 ... and TMZ has learned, he's suing the culprit.
According to the lawsuit -- filed in April last year -- Jacob Sheppard collided with Stefano's car in King County, Washington.
Sheppard admitted to drinking beers and doing shots before the accident -- which left Stefano with two broken arms, a fractured pelvis, and other serious injuries. Sheppard was charged with two counts of vehicular assault and served more than a year behind bars.
Stefano's lawsuit is ongoing.