How Cute Is He???

Jealous!

Leighton Meester‘s boyfriend Sebastian Stan is seriously so adorable.

The Gossip Girl star and her super cute boyfriend partied it up in Vegas over the weekend, where Meester gave a surprise performance at the Hard Rock’s Body English nightclub!

Leighton performed a couple of tracks for the rowdy crowd with DJ Clinton Sparks on Saturday before calling it a night.

Her hot boyfriend must be so proud!

[Image via Scott Berry/Hard Rock Hotel & Casino..]