'Who's Brandi Glanville?'
If Gerard Butler really did have mind-blowing sex with "Real Housewives of Beverly Hills" star Brandi Glanville -- as she proudly claims -- he doesn't remember it ... asking TMZ, "Who's Brandi Glanville?"
In case you didn't know ... Brandi -- Eddie Cibrian's ex-wife -- recently appeared on a talk show, announcing she once bumped uglies with Gerard for an entire week ... and it was so good, she rated him an 11 out of 10.
But either Butler has so much good sex, he can't remember every bangmates's name -- or Brandi's lying. Both are equally plausible.