Pro wrestling superstar Jon Moxley -- formally known as Dean Ambrose -- is hours away from making his return to the U.S. indie circuit ... and the dude is FIRED UP!!
"I feel like I'm 18 again," Moxley tells TMZ Sports ... "I'm just so excited, just chomping at the bit to get back in the ring!"
Moxley was a HUGE star for years with WWE -- a former world champion who was 1/3 of "The Shield," along with Roman Reigns and Seth Rollins.
But his WWE contract expired earlier this year -- so he decided to pursue other options using the "Jon Moxley" moniker he created before his WWE days.