Bare-Butt Babe -- Guess Whose (Blurred) Tan Lines!

Another day, another dollar and another sexy star who's dropped her blouses ... and her trousers! Can you guess who she is?!

She knows a thing or two about Robin Thicke's "Blurred Lines" ... and she acted alongside Ben Affleck in the movie "Gone Girl."

Hit the gallery for the reveal and then see if you can score the "Gone Girl" trivia ...