"Real Housewives of Beverly Hills" star Taylor Armstrong celebrated her 40th birthday this weekend in Las Vegas -- and she did it by showing off a lot of skin!

Armstrong slipped her tiny body into a bikini at Liquid Pool Lounge at Aria Resort & Casino on Saturday, where she mingled with the crowd wearing gold YSL heels.

While she wasn't photographed with husband Russell -- who she was rumored to have split from back in May -- we hear he did attend the bash with her.

Check out all the party pics!