Guess Whose Rock Hard Ab Crack!

Can you guess which sexy star put her rockin' crack on full display in this eye-popping photo?

This celebrity fitness trainer has no shame in her "fit gurl" game ... The shredded star recently took her body goals to her 1 million Instagram followers -- donning this tropical two-piece.

Showin' off her fit physique, this fitness queen -- who notoriously changed Kim Kardashian's bod with her intense workout regime -- modeled several angles of her washboard abs!

Hit up our gallery above and see if you can score the unknown gym junkie in question!

Click here for info about our online advertising practices.