Kyle Richards -- Real Cougars of Beverly Hills Gone Wild

Kyle Richards and her rich friends were ON THE LOOSE this week ... partying at a West Hollywood nightclub like girls 1/3 their age.

The "Real Housewives of Beverly Hills" star hit up iconic gay bar The Abbey on Thursday night to celebrate a friend's birthday ... and to do some risque table dancing.

According to our sources, Kyle and co. arrived around 11:00 PM and stayed til closing at 2 AM ... so, hardly what you'd call a rager.

We're told Richards is quite the barfly -- at the Abbey, anyway ... where she frequently sips on margs (Skinny Girl, we're sure) and is known for leaving fat tips.