Last week, the track broke the US airplay record, gaining 11, 816 spins over the course of a week.
Behind Perry, Eminem rockets into the chart at number two with Rihanna-featured track 'Love The Way You Lie'. The song is taken from his new album Recovery, which debuted at number one on the US album chart this week.
Elsewhere, Lady GaGa slips from seven to nine with 'Alejandro', while Jason Derulo jumps from 16 to ten with 'Ridin' Solo'.
Further down the chart, Selena Gomez makes her chart debut with new single 'Round & Round' at 24 and Maroon 5 land at 44 with comeback track 'Misery'.
VV Brown continues to climb the chart with 'Shark In The Water', jumping from 70 to 67, while Miley Cyrus debuts at 75 with 'Stay'.
The top ten singles in full (click where possible for our reviews):
1. (1) Katy Perry: 'California Gurls'
2. (-) Eminem ft. Rihanna: 'Love The Way You Lie'
3. (2) Usher: 'OMG'
4. (3) B.o.B ft. Eminem & Haley Williams: 'Airplanes'
5. (4) Travie McCoy ft. Bruno Mars: 'Billionaire'
6. (10) Drake: 'Find Your Love'
7. (8) Mike Ponser: 'Cooler Than Me'
8. (6) Ke$ha: 'Your Love Is My Drug'
9. (7) Lady GaGa: 'Alejandro'
10. (16) Jason Derulo: 'Ridin' Solo'