The pop princess donned hot pink chaps and a hot pink cowboy hat to match her hot pink hair. She wore a cow-print, midriff-baring top and pigails, as well.
Perry partied the night away with husband Russell Brand -- who dressed as an Indian -- her brother David, and her sister Angela, reports AceShowbiz.
The celebrity guest list included Adam Lambert, Anna Faris, Chris Pratt, and Robyn.
Adam and his boyfriend dressed up as Dances with the Moon and Dances with the Sun and Robyn went as a cactus.
When guests arrived, they hopped on a horse-drawn wagon with haystack seating. Hired cowboys twirled lassos and a Dolly Parton impersonator serenaded them through the night.
Party-goers chowed down on BBQ meats, corn on the cob, and apple pie a la mode -- all Southern comfort food favorites.
The party also featured a mechanical bull -- which the daring birthday girl rode -- and a photo booth, according to the gossip site.
Perry's actual birthday fell on Oct. 25. At the time, she was on the international leg of her California Dreams tour. She celebrated in London at the Electric Cinema where she and a few friends watched Ghostbusters.
Katy Perry has been on fire lately.
In August, she was proclaimed the first female artist to ever have five #1 singles from one album on the Billboard Hot 100 chart for two consecutive weeks. At the 2011 MTV Video Music Awards she got 10 nominations -- the most of the ceremony and the only singer in history to have four different music videos in multiple categories.
She just released her video for The One that Got Away off her Teenage Dream album.
View tons of photos from Katy Perry's Wild birthday bash at TheCobraSnake.