Chyna -- Collapses at Porn Convention

Former wrestling superstar Chyna collapsed in front of the main stage at a XXX convention in Miami moments ago ... TMZ has learned.

Sources at the scene tell us ... Chyna was hanging out at the 2012 Exxxotica Expo when she suddenly dropped to floor.

We're told several people rushed over to help ... and carried Chyna out of the expo and into a nearby hotel where she's now resting.

Sources say Chyna was checked out by paramedics at the scene -- who didn't feel the porn star needed to be hospitalized.