The festival’s boss Geoff Ellis revealed the names to the Daily Record, in response to internet rumours about the line-up.
“She [Katy Perry] has great songs and is full of attitude. I saw her hosting the MTV Awards in Liverpool and I just knew she could carry it off,” he added.
Katy Perry will headline the NME/Radio 1 stage on the Saturday (July 11).
T In The Park is set to take place in Balado, near Kinross, between July 10-12.
Keep checking NME.COM for T In The Park 2009 line-up announcements and ticket information.