Jason Aldean -- I'm Banging Brittany Kerr, the Girl Who Broke Up My Marriage

Jason Aldean is dating the "American Idol" alum who broke up his marriage -- and we're told they've been hooking up ever since he filed for divorce.

Brittany Kerr -- the A.I. floozie -- was photographed backstage in the wings of Aldean's concert Friday night ... and now we're told it's official ... they're a couple.

It's pretty stunning ... in September, 2012, the two of them were photographed making out at a bar on the Sunset Strip -- it was so obvious they could be seen from the street.

Aldean said at the time it was a one time deal -- a drunken mistake -- and he took a taxi home alone.

Aldean filed for divorce last May.

So now the question ... did they ever really stop seeing each other? No one is saying, but we do know Kerr was in the crowd at his show on January 10th in Austin.

She didn't make it far on "Idol" but she's clearing home base with Aldean.