We're only on day two of Paris Fashion Week, and already we've had a pretty impressive line-up of celebs gracing the show front rows (Kristen Stewart at Balenciaga made our day yesterday.)
And Vera Wang outfit - consisting of waist-tie top and completely see-through drawstring skirt.
Front row fashion: Katy Perry arriving in Paris wearing sheer Vera Wang. Photo: Rex Features/Splash
So yes, those are her knickers.
It's all very 'Russell Brand Who?' And we kind of love her all the more for it. Girl power and all that. If she wants the world to see her undies, then so be it.
Ms Perry performed a frock swap for the evening, attending a Karl Lagerfeld-hosted dinner in this metallic gold Balmain mini dress.
Quick change: Katy arriving at the Karl Lagerfeld dinner in Paris last night. Photo: Splash
Girl's got a good figure.
Check out Katy getting seriously glam in the latest issue of V magazine.
Feast your eyes on more of KP's outlandish style sense in the gallery below: