Paws up, little monsters! Lady Gaga is throwing the Mayhem Ball Tour this summer. The pop icon will kick off the tour in Las ...

Katy Perry supported Lady Gaga at her Mexico City concert on Sunday, April 27, days after Perry launched her Lifetimes Tour.

Katy Perry loves sharing her woman's world with Lady Gaga. In the crowd at Mother Monster's ¡Viva La Mayhem! concert in ...

Lady Gaga will embark on an arena tour this summer. (Kevin Mazur/Getty Images for Coachella) ...