Mark Ballas and Pia


9/15/2011 5:15 AM PDT BY TMZ STAFF

The relationship they said would never last ... didn't last.

"Dancing with the Stars" pro Mark Ballas and "American Idol" hottie Pia Toscano have officially broken up ... according to  The split is said to be "mutual."

Mark is currently training with his "Dancing" partner Kristin Cavallari ... and Pia ... is ... um ... well, she's still hot.