Unpredictable Olly Murs feat. Louisa Johnson
The 'Last Friday Night (T.G.I.F.)' singer celebrates with a special cake.
Katy's second album 'Teenage Dream' was released on 24th August 2010, which makes it one year old today.
"Happy 1 year birthday to Teenage Dream!" Katy said on Twitter.
"We made history, it's been a beautiful year! SO thankful!"
Katy, who recently dyed her hair pink, is currently on her 'California Dreams' tour in America and is enjoying chart success with single 'Last Friday Night (T.G.I.F.)'.
Check out the photo of Katy's special album birthday cake below...