Guess the Sexy Singer in the Tiny Red Bikini!

This brunette beauty is famous for her voice ... and if you have the guts to hit up her concert, you're in for lots of dancing and noise!

Have you figured out who she is? If not, here are a few clues. Don't be sour, but she's only in her early 20s and already has a few Grammys ...

And with nearly 40 million followers on Instagram, she has a poppin' fan base ... Believe it or not, she writes her own bangers!

So before she goes down under for a dip ... take a good guess who this scuba babe is! If you can score the unknown, well then 'Good 4 U!'