'127 Hours' Amputee -- Off the Hook ... For Alleged Domestic Violence

Just like the time he was removed from the boulder ... Aron Ralston is now a free man -- and even better for him, the charges for allegedly assaulting his girlfriend have been dropped.

TMZ has learned the case against Aron -- the real-life inspiration for the movie "127 Hours" -- has been dismissed ... and we're told it's because prosecutors determined they didn't have enough evidence to convict him.

However, Aron's girlfriend Vita Shannon is still facing two criminal charges for allegedly assaulting Aron in front of their 8-month-old child.