Justina Valentine is 39 and looking great … and if you need receipts, this gallery’s got ’em!

The birthday babe knows exactly how to crank up the heat — and it’s not just the signature red hair, ’cause those barely-there bikinis are doing all the talking and showing off every curve.

Justina’s body confidence is on full blast, keeping it on-brand in fiery red … no matter what corner of the globe she’s posing in.