Which Celeb Is Grabbing Justin Timberlake's Butt?

Fellow star gets a handful while golfing in Vegas with JT, who's joined by Jessica Biel

Hey now!

While Justin Timberlake was getting his golf on in Las Vegas, someone just couldn't keep their hands off JT's tush.

And no, it clearly isn't his on-again girlfriend Jessica Biel (who was also in attendance).

Think you know who's copping a feel of Justin's sexy back(side)? Find out after the jump...

RELATED: Justin and Jessica spotted in Sin City

It's funny guy George Lopez.

The comedian was on hand for the Shriner's Hospital for Children Open, Justin's charity golf tourney, and got himself a handful in between putting.

Jessica Biel was spotted chaffeuring her man around the green earlier today, too.

The couple that plays together, stays together? Looks like that's the case...for now, anyhow!

PHOTOS: Vegas Party Pics