BRITNEY. VEGAS. BIKINI!

We caught a fiiiiiine lookin' Miss Brit at the Bare Pool Lounge at the Mirage today in Vegas -- girl's gettin' her Labor Day weekend on!

And you'll NEVER guess who's hanging around the hotel, trying to insert himself into our pictures so it looks like he's chillin' with Brit ...

Those pictures coming soon! And stay tuned for ANOTHER mystery man who made his way to Britney's side this weekend. And this one's actually cute! Stay tuned! ...