Sia's Face -- 'Chandelier' Singer: I've Got Nothing To Hide!!

Finally ... we can see Sia.

The "Chandelier" singer -- who notoriously hides from cameras and even goes as far as performing with her back to the audience -- flashed her pearly whites Wednesday night as she walked into Jimmy Kimmel's studio.

Sia -- who once famously masked her face with a paper bag for the cover of Billboard -- was true to form -- for a performance on Kimmel with face paint.

Sia later ... or not.