EXCLUSIVE

Pittsburgh Steelers running back Chris Rainey has just been fired from the team for allegedly attacking his girlfriend this morning in Florida, TMZ has learned.

Steelers General Manager Kevin Colbert tells us, "Chris Rainey’s actions this morning were extremely disappointing. Under the circumstances and due to this conduct, Chris will no longer be a member of the Pittsburgh Steelers."

As we reported. Chris allegedly flew off the handle this morning in Gainesville when his girlfriend swiped his phone -- and slapped her in the face.

Chris has been charged with battery stemming from the incident. He's currently still in custody.