Mystery solved. The dude is Miley's assistant, Cheyne Thomas. He's also the Dirty Santa on whom Miley was twerking.
Miley Cyrus may have a new guy ... or at least a new guy for the evening.
We got pics of Miley at the opening of Beacher's Madhouse in Vegas after Britney's big opening ... which Miley also attended.
Miley wasn't coy about it ... she clearly wanted everyone to see.
We're trying to figure out who the dude is ... he looks familiar. If anyone has a clue, please send it to us in our contact us box. It's the same guy in both photos ... even though it doesn't look like it.
BTW .. Kellan Lutz was also at Beacher's but left ... without Miley.