Steelers LB Anthony Chickillo is off the hook after he allegedly roughed up his track star girlfriend ... prosecutors tell TMZ Sports she refused to testify against the NFL player, so the charges were dropped.
As we previously reported, Chickillo was arrested on Oct. 20 after his GF -- Canadian track star Alysha Newman -- said an argument at a fancy Pennsylvania resort's casino later turned violent in their hotel room.
Newman claimed Chickillo grabbed her by both arms, forced her against the wall and door and eventually threw her to the ground while intending to cause her injury.