Blake Lively, Leighton Meester

As Gossip Girl heads into its final season, the mystery of who's behind the titular blog that has plagued the Upper East Siders for years will finally be revealed!

"For five years, that's the secret she said she'd never tell," executive producer Sara Goodman says, before executive producer Stephanie Savage adds: "But this year, she's telling."

Gossip Girl Promo: Who's getting exposed? Who's getting slapped? And who's getting hitched?!

Who do you think Gossip Girl is? Blake Lively, Leighton Meester and the rest of the cast share their best guesses as to who she (or he!) is. Check out the video below:

Gossip Girl returns Monday at 9/8c on The CW.