Burn! Not cool, John.

Gossip Girl actress Michelle Trachtenberg is apparently "smitten" with ladies' man John Mayer, a source tells the NY Post.

The two partied at Soho House in LA recently and a witness claims Michelle was acting "bouncy and flirty" around John, but he "seemed too cool for school." I mean, really!

"They've known each other for years," says Michelle's rep, adding that the pair chatted for a few minutes before resuming dinner with her fam.

Probably bogus that Michelle was flirting, but still! This just confirms that John is definitely too cool for school.